United States Office of Water EPA 822-R-13-001

Environmental Protection 4304T April 2013

Agency

AQUATIC LIFE AMBIENT WATER 

QUALITY CRITERIA FOR 

AMMONIA – FRESHWATER 

2013
ii

EPA-822-R-13-001

Aquatic Life 

Ambient Water Quality Criteria For 

Ammonia – Freshwater

2013

April 2013

U.S. Environmental Protection Agency

Office of Water

Office of Science and Technology

Washington, DC
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TABLE OF CONTENTS

TABLE OF CONTENTS............................................................................................................... iii

LIST OF TABLES...........................................................................................................................v

LIST OF FIGURES ....................................................................................................................... vi

LIST OF APPENDICES............................................................................................................... vii

FOREWORD............................................................................................................................... viii

ACKNOWLEDGMENT................................................................................................................ ix

EXECUTIVE SUMMARY .............................................................................................................x

ACRONYMS............................................................................................................................... xiii

INTRODUCTION AND BACKGROUND ....................................................................................1

PROBLEM FORMULATION.........................................................................................................4

Overview of Stressor Sources and Occurrence........................................................................... 5

Environmental Fate and Transport of Ammonia in the Aquatic Environment........................... 6

Mode of Action and Toxicity...................................................................................................... 8

Assessment Endpoints ................................................................................................................ 9

Measures of Effect.................................................................................................................... 10

Acute measures of effect....................................................................................................... 11

Chronic measures of effect ................................................................................................... 12

Chronic averaging period of 30 days.................................................................................... 13

Ammonia toxicity data fulfilling minimum data requirements ............................................ 14

Conceptual Model..................................................................................................................... 16

Conceptual diagram .............................................................................................................. 17

Analysis Plan ............................................................................................................................ 19

EFFECTS ANALYSES FOR FRESHWATER AQUATIC ORGANISMS.................................21

Acute Toxicity to Aquatic Animals.......................................................................................... 21

Summaries of studies used in acute criterion determination................................................. 24

Chronic Toxicity to Freshwater Aquatic Animals.................................................................... 31

Summaries of studies used in chronic criterion determination............................................. 34

The National Criteria for Ammonia in Fresh Water................................................................. 40

Acute criterion calculations .................................................................................................. 40

Chronic criterion calculations............................................................................................... 46

Additional explanation and justification supporting the 2013 temperature and pH-dependent 

calculations and criteria magnitudes..................................................................................... 50

Protection of downstream waters.......................................................................................... 51

Considerations for site-specific criteria derivation ............................................................... 52

EFFECTS CHARACTERIZATION .............................................................................................52

Freshwater Acute Toxicity Data ............................................................................................... 53

Acute toxicity data for freshwater mussels and non-pulmonate (gill-bearing) snails........... 53

Freshwater Chronic Toxicity Data............................................................................................ 56

Use of 28-day juvenile unionid mussel data ......................................................................... 56

28-day toxicity data for freshwater snails............................................................................. 56
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28-day toxicity data for Hyalella azteca: Minimum Data Requirement Number 5.............. 57

Reconsideration of the chronic toxicity data available for aquatic insects: Minimum Data 

Requirement Number 6......................................................................................................... 59

New chronic toxicity data for salmonid species and derivation of a GMCV for

Oncorhynchus: Minimum Data Requirement Number 1...................................................... 59

Another order of insect or a phylum not already represented: Minimum Data Requirement 

Number 8 .............................................................................................................................. 61

Protection of Endangered Species ............................................................................................ 62

Key acute toxicity data for listed species.............................................................................. 62

Key chronic toxicity data for listed species.......................................................................... 64

Comparison of 1999, 2009, and 2013 Criteria Values ............................................................. 65

Comparison of statistical approaches to develop the chronic criterion: EC20 vs. MATC... 68

UNUSED DATA ...........................................................................................................................68

REFERENCES ..............................................................................................................................70
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LIST OF TABLES

Table 1. Summary of Assessment Endpoints and Measures of Effect Used in Criteria 

Derivation for Ammonia....................................................................................................13

Table 2. 1985 Guidelines Minimum Data Requirements Summary Table Reflecting the 

Number of Species and Genus Level Mean Values Represented in the Acute and 

Chronic Toxicity Datasets for Ammonia in Freshwater. ...................................................15

Table 3. Ranked Genus Mean Acute Values. ...............................................................................27

Table 4. Ranked Genus Mean Chronic Values.............................................................................39

Table 5a. Temperature and pH-Dependent Values of the CMC (Acute Criterion Magnitude) 

– Oncorhynchus spp. Present.............................................................................................44

Table 5b. Temperature and pH-Dependent Values of the CMC (Acute Criterion Magnitude) 

– Oncorhynchus spp. Absent. ............................................................................................45

Table 6. Temperature and pH-Dependent Values of the CCC (Chronic Criterion 

Magnitude).........................................................................................................................49

Table 7. Comparison of the Four Taxa Used to Calculate the FAV and CMC in the 1999, 

2009 Draft and 2013 AWQC. ............................................................................................55

Table 8. Comparison of the Four Taxa Used to Calculate the FCV and CCC in the 1999 

Update, 2009 Draft and the 2013 AWQC..........................................................................67

Table F.1. Species, Genus and Taxon-Specific ACRs for Freshwater Aquatic Animals 

Exposed to Ammonia.......................................................................................................145

Table M.1. Results of Regression Analysis of logLC50 (mg/L total ammonia nitrogen) 

Versus Temperature (°C) for Individual Data Sets on the Temperature Dependence 

of Acute Ammonia Toxicity. ...........................................................................................215

Table M.2. Results of Regression Analysis of log LC50 (mg/L total ammonia nitrogen) 

Versus Temperature (°C) for Pooled Data Sets on the Temperature Dependence of 

Acute Ammonia Toxicity to Fish. ...................................................................................216

Table N.1. Temperature and pH-Dependent Values of the CMC (Acute Criterion 

Magnitude) – Unionid Mussels Present, Oncorhynchus Absent. ....................................233

Table N.2. Acute Data Without Mussels: Comparison of the Four Taxa Used to Calculate 

the FAV and CMC in the 1999 AWQC and this Updated 2013 AWQC Excluding 

Data for Freshwater Unionid Mussels. ............................................................................234

Table N.3. Temperature and pH-Dependent Values of the CMC (Acute Criterion 

Magnitude) – Unionid Mussels Absent and Oncorhynchus Present. ..............................235

Table N.4. Temperature and pH-Dependent Values of the CMC (Acute Criterion 

Magnitude) – Unionid Mussels Absent and Oncorhynchus Absent................................236

Table N.5. 2013 Acute Criterion Recalculations for Site-specific Criteria. ...............................237

Table N.6. Chronic Dataset Without Mussels: Comparison of the Four Taxa used to 

Calculate the CCC in the 1999 AWQC and this Updated 2013 AWQC Excluding 

Data for Freshwater Unionid Mussels. ............................................................................237

Table N.7. Chronic Criterion Recalculations for Site-Specific Criteria. ....................................238

Table N.8. Temperature and pH-Dependent Values of the CCC (Chronic Criterion 

Magnitude) – Mussels Absent and Early Life Stage (ELS) Protection Necessary..........239

Table N.9. Temperature and pH-Dependent Values of the CCC (Chronic Criterion 

Magnitude) – Mussels Absent and Early Life Stage (ELS) Protection not Necessary....240
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LIST OF FIGURES

Figure 1. Fraction of Chemical Species of Ammonia Present with Change in pH (at 25°C).........7

Figure 2: Conceptual Model for Ammonia Effects on Aquatic Animals. ....................................18

Figure 3. Ranked Freshwater Genus Mean Acute Values (GMAVs) with Criterion 

Maximum Concentrations (CMCs)....................................................................................24

Figure 4. Ranked Freshwater Genus Mean Chronic Values (GMCVs) with Criterion 

Continuous Concentrations (CCCs)...................................................................................33

Figure 5a. 2013 Acute Criterion Magnitudes Extrapolated Across a Temperature Gradient 

at pH 7................................................................................................................................43

Figure 5b. 2013 Chronic Criterion Magnitudes Extrapolated Across a Temperature Gradient 

at pH 7................................................................................................................................48

Figure F.1. SMACRs by SMAV Rank. ......................................................................................148

Figure M.1. The Effect of Temperature on Ammonia Toxicity in Terms of Unionized 

Ammonia (DeGraeve et al. 1987)....................................................................................203

Figure M.2. The Effect of Temperature on Acute Ammonia Toxicity in Terms of Total 

Ammonia Nitrogen. .........................................................................................................205

Figure M.3. The Effect of Temperature on pH-Adjusted Acute Ammonia Toxicity in Terms 

of Total Ammonia Nitrogen.............................................................................................206

Figure M.4. The Effect of Temperature on Normalized Acute Ammonia Toxicity in Terms 

of Total Ammonia Nitrogen.............................................................................................210

Figure M.5. The Effect of Temperature on Chronic Ammonia Lethality to Fathead 

Minnows in Terms of Total Ammonia Nitrogen (DeGraeve et al. 1987). ......................211

Figure M.6. Temperature Dependence of Acute Ammonia Toxicity to Invertebrate 

Organisms from Arthur et al. (1987). ..............................................................................221

Figure M.7. Temperature-Dependence of Ammonia ACRs for Fathead Minnows. ..................223

Figure N.1. Comparison of the 2013 CMC Extrapolated Across a Temperature Gradient at 

pH 7 Accounting for the Presence or Absence of Unionid Mussels and the Presence 

or Absence of Oncorhynchus...........................................................................................241

Figure N.2. Comparison of the 2013 CCC Extrapolated Across a Temperature Gradient at 

pH 7 Accounting for the Presence or Absence of Mussels and/or the Need for Early 

Life Stage (ELS) Protection of Fish Species. ..................................................................242
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LIST OF APPENDICES

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals. ..................................................86

Appendix B. Chronic Toxicity of Ammonia to Aquatic Animals. .............................................131

Appendix C. Other Chronic Ammonia Toxicity Data. ...............................................................134

Appendix D. Conversion of Acute Results of Toxicity Tests. ...................................................138

Appendix E. Conversion of Chronic Results of Toxicity Tests..................................................141

Appendix F. Acute-Chronic Ratios (ACRs). ..............................................................................143

Appendix G. Results of the Regression Analyses of New Chronic Data for Unionid 

Mussels. ...........................................................................................................................149

Appendix H. Detailed Descriptions of Select New Acute and Chronic Toxicity Test Data 

Used for Criteria Derivation. ...........................................................................................154

Appendix I. Qualitative Weight-of-Evidence Test Data.............................................................163

Appendix J. Unused Acute Studies Potentially Influential for Freshwater Ammonia Criteria 

Development....................................................................................................................171

Appendix K. Unused Chronic Studies Potentially Influential for Freshwater Ammonia 

Criteria Development.......................................................................................................177

Appendix L. Unused (Non-Influential) Acute and Chronic Studies for Freshwater Ammonia 

Criteria Development – Screened Out Studies with Code List........................................179

Appendix M. 1999 Re-examination of Temperature Dependence of Ammonia Toxicity. ........199

Appendix N. Site-Specific Criteria for Ammonia. .....................................................................225
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FOREWORD

This water quality criteria update provides scientific recommendations to states and tribes 

authorized to establish water quality standards under the Clean Water Act (CWA), to protect 

aquatic life from acute and chronic effects of ammonia in freshwater ecosystems. Under the 

CWA, states and tribes are to establish water quality criteria to protect designated uses. State 

and tribal decision makers retain the discretion to adopt approaches on a case-by-case basis that 

differ from those used in these criteria when appropriate. While this update constitutes United 

States Environmental Protection Agency (EPA) scientific recommendations regarding ambient 

concentrations of ammonia that protect freshwater aquatic life, this update does not substitute for 

the CWA or EPA’s regulations; nor is it a regulation itself. Thus, it cannot impose legally 

binding requirements on EPA, states, tribes, or the regulated community, and might not apply to 

a particular situation based upon the circumstances. EPA may change these criteria in the future, 

as new scientific information becomes available. This document has been approved for 

publication by the Office of Science and Technology, Office of Water, U.S. Environmental 

Protection Agency. Mention of trade names or commercial products does not constitute 

endorsement or recommendation for use.
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ACKNOWLEDGMENT

This 2013 criteria document is an update of the 1999 Update of Ambient Water Quality 

Criteria for Ammonia. The updates described herein were prepared by Lisa Huff (EPA Team 

Leader), Charles Delos, Kathryn Gallagher, and Joe Beaman with written and technical support 

provided by EPA contractor: Great Lakes Environmental Center, Inc. EPA received substantial 

input from Dave Mount, James (Russ) Hockett, Russell Erickson, and Charles Stephan of the 

EPA’s Office of Research and Development (ORD) National Health and Environmental Effects 

Research Laboratory (NHEERL) Mid-Continent Ecology Division, Duluth, MN, and Cindy 

Roberts, ORD Office of Science Policy. Please submit comments or questions to: Lisa Huff, 

U.S. EPA, Mail Code 4304, Washington, DC 20460 (e-mail: huff.lisa@epa.gov).
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EXECUTIVE SUMMARY

EPA has updated the freshwater ammonia aquatic life ambient water quality criteria in 

accord with the provisions of Section 304(a) of the Clean Water Act to revise Ambient Water 

Quality Criteria (AWQC) from time to time in order to reflect the latest scientific knowledge. 

Literature searches for laboratory toxicity tests of ammonia on freshwater aquatic life, published 

from1985 to 2012, identified new studies containing acute and chronic toxicity data acceptable 

for criteria derivation. The acute criterion dataset includes 12 species of aquatic animals

Federally-listed as threatened, endangered or species of concern. In the chronic dataset for 

ammonia, Federally-listed species are represented by three salmonid fish species in the genus 

Oncorhynchus, including sockeye salmon, rainbow trout/steelhead, and the subspecies Lahontan 

cutthroat trout. Data were assessed from the perspective of EPA’s “Guidelines for Deriving 

Numerical National Water Quality Criteria for the Protection of Aquatic Organisms and Their 

Uses” (Stephan et al. 1985).

The 1999 recommended aquatic life criteria for ammonia were based on the most 

sensitive endpoints known at the time: the acute criterion was based primarily on effects on 

salmonids (where present) or other fish, and the chronic criterion was based primarily on 

reproductive effects on the benthic invertebrate Hyalella or on survival and growth of fish early 

life stages (when present), depending on temperature and season.

The 2013 recommended criteria of this document take into account data for several 

sensitive freshwater mussel species in the Family Unionidae that had not previously been tested. 

As noted in the 2009 draft ammonia criteria document, available data indicated that another 

freshwater mollusk taxon, non-pulmonate (gill-bearing) snails, are also sensitive to the effects of 

ammonia (EPA-822-D-09-001). The 2013 criteria include additional data confirming the 

sensitivity of freshwater non-pulmonate snails. Many states in the continental United States have 

freshwater unionid mussel fauna in at least some of their waters (Abell et al. 2000, Williams et 

al. 1993, Williams and Neves 1995). Moreover, approximately one-quarter of approximately 

300 freshwater unionid mussel taxa in the United States are Federally-listed as endangered or

threatened species. Freshwater mussels are broadly distributed across the U.S., as are freshwater 

non-pulmonate snails, another sensitive invertebrate taxon, and both of these groups are now 

included in the ammonia dataset. Thus, the 2013 freshwater acute and chronic aquatic life 

criteria for ammonia will more fully protect the aquatic community than previous criteria, and 
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are represented by a single (non-bifurcated) value each for acute and chronic criteria.

The criteria magnitude is affected by pH and temperature. After analysis of the new data, 

EPA determined that the pH and temperature relationships established in the 1999 ammonia 

criterion document still hold. When expressed as total ammonia nitrogen (TAN), the effect 

concentrations for fish are normalized only for pH, reflecting the minimal influence of 

temperature on TAN toxicity to fish. For invertebrates, TAN effect concentrations are 

normalized for both pH and temperature. At water temperatures greater than 15.7°C, the 2013 

acute criterion magnitude is determined primarily by effects on freshwater unionid mussels. At 

lower temperatures the acute criterion magnitude is based primarily on effects on salmonids and 

other fish. Throughout the temperature range, the 2013 chronic criterion magnitude is 

determined primarily by the effects on freshwater mollusks, particularly unionid mussels.

At an example pH of 7 and temperature of 20°C, the 2013 acute criterion magnitude is 17

mg TAN/L and the chronic criterion magnitude is 1.9 mg TAN/L. At pH 7 and 20°C the 2013

acute criterion magnitude is 1.4-fold lower than the 1999 acute criterion magnitude. At this pH 

and temperature, the 2013 chronic criterion magnitude is 2.4-fold lower than the 1999 chronic 

criterion magnitude. See the Criterion Statements (pages 40-49) for the criterion concentrations 

at other pH and temperature conditions. The decreases in acute and chronic criteria magnitudes 

below those of 1999 reflect the inclusion of the new data discussed above.

The acute criterion duration represents a one-hour average. The chronic criterion 

duration represents a 30-day rolling average with the additional restriction that the highest 4-day 

average within the 30 days be no greater than 2.5 times the chronic criterion magnitude. These 

values are not to be exceeded more than once in 3 years on average.
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Criterion

Duration

1999 AWQC

Update Criteria

Magnitude

2009 Draft AWQC

Update Criteriac

Magnitude

2013 AWQC

Update Criteria 

Magnitude

pH 8.0,

(mg TAN/L)

pH 7.0,

T=20°C

(mg TAN/L)

pH 8.0,

T=25°C

(mg TAN/L)

pH 7.0,

T=20°C

(mg TAN/L)

pH 7.0,

T=20°C

(mg TAN/L)

Acute

(1-hr average) 5.6a

24a2.9 19 17a

Chronic

(30-d rolling 

average)

1.2 4.5b0.26 0.91 1.9*

*Not to exceed 2.5 times CCC or 4.8 mg TAN/L (at pH 7, 20°C) as a 4-day average within the 30-days,

more than once in three years on average.

Criteria frequency: Not to be exceeded more than once in three years on average.

a

Salmonids present

b Based on renormalization of data to pH 7 and 20°C

c Mussels present
xiii

ACRONYMS

ACR Acute-Chronic Ratio

ASTM American Society of Testing and Materials

AWQC Ambient Water Quality Criteria

CCC Criterion Continuous Concentration

CMC Criterion Maximum Concentration

CV Chronic Value (expressed in this document as an EC20 or MATC)

CWA Clean Water Act

ECx Effect Concentration at X Percent Effect Level

LCx Lethal Concentration at X Percent Survival Level

EPA Environmental Protection Agency

ESA Endangered Species Act

FACR Final Acute-Chronic Ratio

FAV Final Acute Value

FCV Final Chronic Value

GMACR Genus Mean Acute-Chronic Ratio

GMAV Genus Mean Acute Value

GMCV Genus Mean Chronic Value

LOEC Lowest Observed Effect Concentration

MATC Maximum Acceptable Toxicant Concentration (expressed mathematically as the 

geometric mean of the NOEC and LOEC)

NOEC No Observed Effect Concentration

SD Sensitivity Distribution

SMACR Species Mean Acute-Chronic Ratio

SMAV Species Mean Acute Value

SMCV Species Mean Chronic Value

TAN Total Ammonia Nitrogen

TRAP EPA’s Statistical Program: Toxicity Relationship Analysis Program (Version 

1.21)

WER Water Effect Ratio
1

INTRODUCTION AND BACKGROUND

National Ambient Water Quality Criteria (AWQC) are established by the United States 

Environmental Protection Agency (EPA) under the Clean Water Act (CWA). EPA will review 

and from time to time revise 304(a) AWQC as necessary to ensure the criteria are consistent with

the latest scientific information. Section 304(a) aquatic life criteria serve as recommendations to 

states and tribes in defining ambient water concentrations that will protect against adverse 

ecological effects to aquatic life resulting from exposure to a pollutant found in water from direct 

contact or ingestion of contaminated water and/or food. Aquatic life criteria address the CWA 

goals of providing for the protection and propagation of fish and shellfish. When adopted into 

state standards, these criteria can become a basis for establishing permit limits and Total 

Maximum Daily Loads (TMDLs). 

EPA first published aquatic life criteria recommendations for ammonia in 1976, followed 

nine years later by the 1985 criteria revision, which used updated procedures and additional 

information. The 1985 acute ammonia criterion was calculated from acute values expressed as

unionized ammonia and normalized for pH (8.0) for all freshwater aquatic animals, and 

temperature (20°C) for freshwater fish only. Because the fraction of total ammonia that is 

unionized varies with pH and temperature, the 1985 toxicity data normalizations with unionized

ammonia were necessarily structured differently than the current document’s normalizations with 

total ammonia nitrogen. Because the 1985 chronic toxicity dataset was more limited than is 

available now, the 1985 chronic criterion was calculated by dividing the Final Acute Value by an 

acute-chronic ratio (ACR). The 1985 acute and chronic criteria concentrations were 19 and 1.2

mg/L expressed as total ammonia nitrogen at pH 7 and temperature 20°C for salmonids or other 

coldwater species present (e.g., rainbow trout). The durations for these criteria were one-hour 

(acute) and four-day (chronic) averaging periods. The 1985 freshwater acute criterion dataset 

was composed of acute values from tests involving 41 species (29 fish and 12 invertebrate) 

representing 34 genera (18 fish and 16 invertebrate). The data available for invertebrates at the 

time indicated they were not among the more acutely-sensitive organisms to ammonia. 

In 1999 EPA revised the 1985 freshwater ammonia criteria to incorporate newer data, 

better models, and improved statistical methods. For its acute criterion, the revision included a 

re-examination of the temperature and pH relationships underlying the 1985 acute criterion,

reworked from the perspective of total ammonia nitrogen rather than unionized ammonia. For its 
2

chronic criterion, EPA developed relationships for formulating a seasonal, pH- and temperaturedependent relationship, in part because the chronic criterion was based on endpoints that might 

not be of concern during cold-season conditions (e.g., fish early life stages). EPA analyzed all of 

the freshwater chronic data used in the 1985 criteria document as well as newer chronic data and 

was able to directly calculate a chronic criterion instead of calculating it from the acute criterion 

with an ACR. EPA did not conduct a comprehensive literature search for and critical review of 

all of the acute toxicity data published after 1985, but focused on the chronic criteria, in response 

to scientific issues raised by the public. Thus, the 1999 acute criterion relied on acute tests 

reported in Table 1 in the 1985 criteria document, supplemented by a limited number of newer 

studies relevant to the revised pH relationship.

The 1999 criteria were based on the most sensitive endpoints known at the time: the acute 

criterion was based primarily on effects on fish throughout the temperature range, and the 

chronic criterion was based primarily on effects on benthic macroinvertebrates or fish early life 

stages (when present), depending on temperature and season. For the 1999 acute criterion the 

effect concentrations for fish were normalized for pH only, reflecting the minimal influence of 

temperature on total ammonia toxicity to fish. The 1999 acute criterion was not adjusted for 

temperature because invertebrates that were included in the dataset, mollusks included, were not 

among the species highly sensitive to ammonia, thus, the invertebrate temperature slope did not 

affect the formulation of the 1999 acute criterion. The 1999 chronic criterion was adjusted for 

pH for fish and for pH and temperature for invertebrates. The chronic averaging period was 

increased from a 4- to a 30-day average in the 1999 update; the rationale for this change was 

based on analysis of chronic data from fathead minnow laboratory tests of different exposure 

durations and exposure concentrations with “limited variability” (see detailed discussion in the 

Problem Formulation of this document under Chronic Measures of Effect). For chronic toxicity, 

the 1999 updated dataset consisted of nine values representing four invertebrate and five fish 

genera. Two of the four most chronically sensitive species were invertebrates (the benthic 

amphipod Hyalella azteca and the bivalve mollusk, Musculium transversum). Missing were 

representative chronic values for the genus Oncorhynchus (salmonid) and an insect genus, 

although in both of these cases the calculation of the fifth percentile directly from the GMCVs in 

Table 5 of the 1999 update was deemed to adequately protect the freshwater aquatic community. 
3

In 2004 EPA published a Federal Register Notice indicating its intent to re-evaluate the 

freshwater ammonia criteria and requesting new information on ammonia toxicity to freshwater 

mussel species in the Family Unionidae. This action was taken in response to concerns from 

U.S. Fish and Wildlife Service (USFWS) and mussel researchers about the sensitivity of unionid 

mussels to ammonia (summarized by Augspurger et al. 2003). The current document takes into 

account all such data, new toxicity data obtained by a search of the literature for all other species, 

and updated analyses of tests previously included in the 1999 document. 

In 2009, EPA published a draft ammonia criteria document that included all available 

new data on the toxicity of ammonia to freshwater mussels (EPA-822-D-09-001). The draft 

2009 document incorporated new toxicity data in the acute and chronic dataset while retaining

the relationships describing the influence of pH and temperature on ammonia toxicity established 

in the 1999 criteria. The 2009 acute dataset represented 67 genera, including 12 species of 

freshwater mussels, compared to only 34 genera in the 1999 AWQC. Freshwater bivalve 

mollusks and snails were the predominant groups of genera ranked in the lowest (most sensitive) 

quartile, and the four most acutely sensitive genera were all bivalves. The 2009 chronic dataset 

incorporated two new fish species and new data for three freshwater mussel species, which 

represented two of the four most sensitive genera. The draft 2009 criteria recommendations

were bifurcated, with a set of acute and chronic criteria values for waters with mussels present 

that reflects their greater sensitivity to ammonia, and a different set of criteria values for waters 

where mussels are absent. Including the new acceptable data for freshwater unionid mussels, the 

draft 2009 acute and chronic criteria magnitudes, respectively, were 19 and 0.91 mg TAN/L

adjusted to pH 7.0 and 20°C.

For this 2013 update, EPA conducted a new literature search for both acute and chronic

toxicity data and reanalyzed data considered in the 1999 criteria and the 2009 draft. EPA 

reviewed results from this literature search and reanalysis of previously considered data to 

identify data from laboratory toxicity tests that quantify the adverse effects of ammonia on 

freshwater aquatic life (amphibians, fishes, and macroinvertebrates), with particular attention 

given to tests conducted with freshwater unionid mussels and non-pulmonate snails, since such 

data were not available for many of these species previously. While unionid mussel species are 

not prevalent in some waters, such as in the arid west, non-pulmonate snails are broadly 

distributed across the U.S. Thus, considering that freshwater unionid mussels are among the 
4

most sensitive genera in the dataset, and that all states have at least one freshwater unionid 

mussel or bivalve mollusk, or non-pulmonate snail species, another relatively sensitive mollusk 

group, native or present in at least some of their waters, EPA is recommending a single national 

acute and a single national chronic criterion be applied to all waters rather than different criteria 

based on the presence or absence of mussels.

EPA also conducted a separate search and analysis of any relevant new data specific for 

freshwater mussels to evaluate whether the existing pH-acute TAN toxicity relationship 

established in the 1999 update document similarly applies to this group of invertebrates. Based 

on the results of the literature review, EPA concludes that the same pH and temperature 

relationships used to account for the influence of these two abiotic factors on ammonia toxicity 

in the 1999 AWQC document are still applicable (e.g., see Additional Explanation and 

Justification Supporting the 2013 Temperature and pH-Dependent Calculations and Criteria 

Magnitudes section for additional details, pg. 50).

PROBLEM FORMULATION

Problem formulation provides a strategic framework for water quality criteria 

development by focusing the effects assessment on the most relevant chemical properties and 

endpoints. The structure of this effects assessment is consistent with EPA’s Guidelines for 

Ecological Risk Assessment (U.S. EPA 1998) 

This ecological effects assessment defines scientifically-defensible water quality criteria 

values for ammonia under section 304(a)(1) of the Clean Water Act. The goal of the Clean 

Water Act is to protect and restore the biological, chemical and physical integrity of waters of 

the U.S. Clean Water Act Section 304(a)(1) requires EPA to develop criteria for water quality 

that accurately reflect the latest scientific knowledge. These criteria are based solely on data and 

best professional scientific judgments on toxicological effects. Criteria are developed following 

the guidance outlined in the Agency’s Guidelines for Deriving Numerical National Water 

Quality Criteria for the Protection of Aquatic Organisms and Their Uses (Stephan et al. 1985).

Once Section 304(a) water quality criteria are finalized, states and authorized tribes may 

adopt the criteria into their water quality standards to protect designated uses of water bodies. 

States and tribes may also modify the criteria to reflect site-specific conditions or use other 
5

scientifically-defensible methods to develop standards. Water quality standards are subsequently 

approved by EPA.

Overview of Stressor Sources and Occurrence

Ammonia is considered one of the most important pollutants in the aquatic environment 

not only because of its highly toxic nature, but also its ubiquity in surface water systems (Russo 

1985). Ammonia is produced for commercial fertilizers and other industrial applications using a 

reaction that converts atmospheric nitrogen to ammonia using hydrogen obtained from methane

(natural gas) under high heat and pressure; the ammonia gas is then compressed under low 

temperature and stored in an anhydrous liquid form (Appl 1999). In agriculture, ammonia is 

used both directly (in anhydrous form), as well as a precursor for other nitrogen-based fertilizers 

such as ammonium nitrate, ammonium phosphate, urea, and ammonium sulfate (Environment 

Canada 2010). The agricultural industry uses approximately 90% of the U.S. annual domestic 

ammonia production (USGS 2004). Ammonia also has numerous industrial applications, 

including use as a protective atmosphere and as a source of hydrogen in metal finishing and 

treating applications (e.g., nitriding; Appl 1999), as well as many other uses in the chemical 

industry including the production of pharmaceuticals (Karolyi 1968) and dyes (Appl 1999). The 

petroleum industry utilizes ammonia for processing of crude oil and in corrosion protection (U.S. 

EPA 2004). Ammonia is also used in the mining industry for metals extraction (U.S. EPA 

2004). Natural sources of ammonia include the decomposition or breakdown of organic waste 

matter, gas exchange with the atmosphere, forest fires, animal waste, the discharge of ammonia 

by biota, and nitrogen fixation processes (Environment Canada 1997; Environment Canada 

2010; Geadah 1985). 

Ammonia can enter the aquatic environment via anthropogenic sources or discharges 

such as municipal effluent discharges, agricultural runoff, and natural sources such as nitrogen 

fixation and the excretion of nitrogenous wastes from animals. While much of the early 

information regarding lethal concentrations of ammonia was driven by the consequences of 

ammonia buildup in aquaculture systems (i.e., fish culture ponds, hatchery raceways, and fish 

holding and transporting tanks), the introduction of ammonia into surface water systems from 

industrial processes, agricultural runoff, and sewage effluents has received considerable attention 

since the 1980s (Alabaster and Lloyd 1980; U.S. EPA 1985). Many effluents have to be treated 
6

extensively in order to keep the concentrations of ammonia in surface waters from being 

unacceptably high. In 2011, there were approximately 4.7 million pounds (lbs.) of ammonia 

documented as discharged from all reporting industries to surface waters (U.S. EPA 2011). In 

2010, industrial releases of ammonia to ten large aquatic ecosystems (e.g., Chesapeake Bay, 

Puget Sound, Great Lakes) were reported to total approximately 1.3 million lbs. (U.S. EPA 

2010). 

Environmental Fate and Transport of Ammonia in the Aquatic Environment

Ammonia (NH3) is formed in the natural environment by the fixation of atmospheric 

nitrogen and hydrogen by diazotrophic microbes, such as cyanobacteria (Latysheva et al. 2012). 

Trace amounts are also produced by lightning (Noxon 1976). Decomposition of manure, dead 

plants and animals by bacteria in the aquatic and terrestrial environments produce ammonia and 

other ammonium compounds through conversion of nitrogen during decomposition of tissues in 

a process called ammonification (ATSDR 2004; Sylvia 2005). In the aquatic environment, 

ammonia is also produced and excreted by fish. The chemical form of ammonia in water 

consists of two species, the more abundant of which is the ammonium ion (NH4

+

) and the less 

abundant of which is the non-dissociated or unionized ammonia (NH3) molecule; the ratio of 

these species in a given aqueous solution is dependent upon both pH and temperature (Emerson 

et al. 1975; Erickson 1985; Thurston 1988; Whitfield 1974; Wood 1993). Chemically, ammonia 

in an aqueous medium behaves as a moderately strong base with pKa values ranging from 

approximately 9 to slightly above 10 as a function of temperature and ionic strength (Emerson et 

al. 1975; Whitfield 1974). In general, the ratio of unionized ammonia to ammonium ion in fresh 

water increases by 10-fold for each rise of a single pH unit, and by approximately two-fold for 

each 10°C rise in temperature from 0-30°C (Erickson 1985). Basically, as values of pH and 

temperature tend to increase, the concentration of NH3 increases and the concentration of NH4

+

decreases. 

The ionized ammonium ion (NH4

+

) and unionized ammonia molecule (NH3) are 

interrelated through the chemical equilibrium NH4

+

- OH-↔ NH3·H2O↔ NH3+H2O (Emerson et 

al. 1975; Russo 1985). The concentration of total ammonia (often expressed on the basis of 

nitrogen as total ammonia nitrogen or TAN) is the sum of NH4

+

and NH3 concentrations. It is 

total ammonia that is analytically measured in water samples. To estimate the relative 
7

concentrations of NH4

+

and NH3 from total ammonia, Emerson et al.'s (1975) formulas are 

recommended (Adams and Bealing 1994; Alabaster and Lloyd 1980; Richardson 1997; Russo 

1985). Figure 1 (below) shows the chemical speciation of ammonia over a range of pH levels in 

ambient waters at 25°C. It depicts the 10-fold increase in the ratio of unionized ammonia to 

ammonium ion in fresh water for each rise of a single pH unit as described above. This increase 

in unionized ammonia with increased pH is one hypothesis explaining why toxicity of total 

ammonia increases as pH increases.

Figure 1. Fraction of Chemical Species of Ammonia Present with Change in pH (at 25°C).

Each separate fraction of total ammonia can be calculated in freshwater from the 

Henderson-Hasselbach equation if the pH and pKa are known:

NH4

+

= Total ammonia/(1+ antilog (pH-pKa)) = Total ammonia – NH3 (Wood 1993)

and,

pKa = 0.09018 + (2729.92/(273.2 + T)) (Emerson et al. 1975)

where T is temperature in °C. 
8

Mode of Action and Toxicity

Ammonia is unique among regulated pollutants because it is an endogenously produced 

toxicant that organisms have developed various strategies to excrete, which is in large part by 

passive diffusion of unionized ammonia from internal organs, such as the gills in fish. High 

external unionized ammonia concentrations reduce or reverse diffusive gradients and cause the 

buildup of ammonia in internal tissues and blood. Unionized ammonia may cause toxicity to 

Nitrosomonas spp. and Nitrobacter spp. bacteria, inhibiting the nitrification process (Russo 

1985). Bacterial inhibition can result in the increased accumulation of ammonia in the aquatic 

environment, thereby intensifying the toxicity to beneficial bacteria and aquatic animals (Russo 

1985).

The toxic action of unionized ammonia on aquatic animals, particularly in sensitive fish, 

may be due to one or more of the following causes: (1) proliferation in gill tissues, increased 

ventilation rates and damage to the gill epithelium (Lang et al. 1987); (2) reduction in blood 

oxygen-carrying capacity due to progressive acidosis (Russo 1985); (3) uncoupling oxidative 

phosphorylation causing inhibition of production and depletion of adenosine triphosphate (ATP) 

in the brain (Camargo and Alonso 2006); (4) and the disruption of osmoregulatory and 

circulatory activity disrupting normal metabolic functioning of the liver and kidneys (Arillo et.

al.1981; Tomasso et al. 1980).

Among invertebrates, studies testing ammonia toxicity to bivalves, and particularly 

studies with freshwater mussels in the family Unionidae, have demonstrated their sensitivity to 

ammonia (Augspurger et al. 2003; Wang et al. 2007a, b; Wang et al. 2008). Toxic effects of

unionized ammonia to both freshwater and marine bivalves include reduced opening of valves 

for respiration and feeding (Epifanio and Srna 1975); impaired secretion of the byssus, or 

anchoring threads in bivalves (Reddy and Menon 1979); reduced ciliary action in bivalves (U.S. 

EPA 1985); depletion of lipid and carbohydrate stores leading to metabolic alteration (Chetty 

and Indira 1995) as well as mortality (Goudreau et al. 1993). These negative physiological 

effects may lead to reductions in feeding, fecundity, and survivorship, resulting in decreased

bivalve populations (Alonso and Camargo 2004; Constable et al. 2003).
9

Assessment Endpoints

Assessment endpoints are defined as “explicit expressions of the actual environmental value 

that is to be protected” and are defined by an ecological entity (species, community, or other 

entity) and its attribute or characteristics (U.S. EPA 1998). Assessment endpoints may be 

identified at any level of organization (e.g., individual, population, community). In the context

of the Clean Water Act, aquatic life criteria for toxics are typically determined based on the 

results of toxicity tests with aquatic organisms in which unacceptable effects on growth, 

reproduction, or survival occurred. This information is aggregated into a species sensitivity 

analysis that evaluates the impact on the aquatic community. Criteria are designed to be 

protective of the vast majority of aquatic animal species in an aquatic community (i.e., 

approximately 95

th percentile of tested aquatic animals representing the aquatic community). As 

a result, health of the aquatic ecosystem may be considered as an assessment endpoint indicated 

by survival, growth, and reproduction. To assess potential effects on the aquatic ecosystem by a 

particular stressor, and develop 304(a) aquatic life criteria under the CWA, EPA typically 

requires the following:

 Acute toxicity test data (mortality, immobility, loss of equilibrium) for aquatic animals

from a minimum of eight diverse taxonomic groups. The diversity of tested species is 

intended to ensure protection of various components of an aquatic ecosystem. The acute 

freshwater toxicity testing requirement is fulfilled with the following eight minimum data 

requirements: 

 the family Salmonidae in the class Osteichthyes 

 a second family in the class Osteichthyes, preferably a commercially or 

recreationally important warmwater species (e.g., bluegill, channel catfish, 

etc.)

 a third family in the phylum Chordata (may be in the class Osteichthyes or 

may be an amphibian, etc.)

 a planktonic crustacean (e.g., cladoceran, copepod, etc.)

 a benthic crustacean (e.g., ostracod, isopod, amphipod, crayfish, etc.)

 an insect (e.g., mayfly, dragonfly, damselfly, stonefly, caddisfly, 

mosquito, midge, etc.)
10

 a family in a phylum other than Arthropoda or Chordata (e.g., Rotifera, 

Annelida, Mollusca, etc.)

 a family in any order of insect or any phylum not already represented

 Chronic toxicity test data (longer-term survival, growth, or reproduction) are required for 

a minimum of three taxa in order to use acute to chronic ratios to estimate a chronic 

value, which involves having acceptable chronic toxicity data for the following:

 at least one fish

 at least one invertebrate

 at least one chronic test being from an acutely-sensitive species 

However, since acceptable chronic values were available for ammonia for all eight

minimum data requirements, the chronic criterion was derived following the same genus 

level sensitivity distribution (SD) approach used to calculate the acute criterion (see 1985 

Guidelines for additional detail).

 The Guidelines also require at least one acceptable test with a freshwater alga or vascular 

plant. If plants are among the aquatic organisms most sensitive to the material, results of 

a plant in another phylum should also be available. The data available on the toxicity of 

ammonia to freshwater plants indicate that plants are approximately two orders of 

magnitude less sensitive than the aquatic animals tested. Therefore, plant endpoints were 

not used in criteria derivation.

Measures of Effect

Each assessment endpoint requires one or more “measures of ecological effect,” which 

are defined as changes in the attributes of an assessment endpoint itself or changes in a surrogate 

entity or attribute in response to chemical exposure. Ecological effect data are used as measures 

of direct and indirect effects to biological receptors. The measures of effect selected represent 

the growth, reproduction, and survival of the organisms. 

The amount of toxicity testing data available for any given pollutant varies significantly, 

depending primarily on whether any major environmental issues are raised due to interpretation 
11

of those data. An in-depth evaluation of available data is performed by EPA to determine test 

acceptability. 

Acute measures of effect

Acute measures of effect used for organisms in this document are the LC50 and EC50. LC 

stands for “Lethal Concentration” and the LC50 is the concentration of a chemical that is 

estimated to kill 50% of the test organisms. EC stands for “Effective Concentration” and the 

EC50 is the concentration of a chemical that is estimated to produce a specific effect in 50% of 

the test organisms. 

As part of the evaluation of new acute data for ammonia, studies submitted using 

glochidia, the larval life stage of freshwater mussels in the family Unionidae, were reviewed for 

acceptability for use in the ammonia criteria development. In 2006 a new ASTM method was 

published for toxicity tests with glochidia. However, at the time of the 2009 draft revised criteria 

for ammonia, EPA and external peer reviewers were concerned that information was unavailable 

to determine whether the tests with glochidia were ecologically relevant. Specifically, the 

appropriate duration of the tests (24, 48, or 96 hrs) was uncertain because it was unclear how the 

tests of various durations related to the viability of this short parasitic life stage and its ability to 

successfully infect a fish host upon encountering the appropriate fish species. Since that time, 

studies by Bringolf et al. (2013) have resulted in the recommendation of a maximum test 

duration of 24 hours for glochidia corresponding with the ecologically relevant endpoint of 

infectivity for this parasitic life stage. EPA agreed with this recommendation and decided to 

include glochidia tests in the criterion dataset for test data with durations of up to 24 hours with

survival of glochidia at the end of 24 hours of at least 90% in the control treatment. In addition, 

to account for species of mussels whose glochidia might not be expected to be viable at 24 hours

(i.e., potentially mantle lure strategists), EPA examined available tests with glochidia that were

conducted for 24 hours that included testing for viability at 6, 12, and 18 hours. If the viability 

was less than 90% at 24 hours in the control animals, then the next longest duration less than 24 

hours that had at least 90% survival in the control, was considered acceptable for use in deriving 

the ammonia criteria.
12

Chronic measures of effect

Chronic measures of effect are EC20, NOEC, LOEC, and MATC. EC20 values were used 

to estimate a low level of effect observed in chronic datasets that are available for ammonia (see 

U.S. EPA 1999). EC20 is the concentration of a chemical that is estimated to result in a 20

percent effect in a chronic endpoint (e.g., growth, reproduction, and survival) of the test 

organisms.

The NOEC (i.e., “No-Observed -Effect-Concentration”) is the highest test concentration 

at which none of the observed effects are statistically different from the control. The LOEC (i.e.,

“Lowest-Observed- Effect-Concentration”) is the lowest test concentration at which observed 

effects are found to be statistically different from the control. The MATC is the calculated 

geometric mean of the NOEC and LOEC.

For life-cycle (LC) and partial life-cycle (PLC) tests, the toxicological variables used in 

regression analyses were survival, embryo production, and embryo hatchability. For early lifestage (ELS) tests with fishes, the endpoints used were embryo hatchability, fry/larval survival, 

and fry/larval growth. If ammonia reduced both survival and growth, the product of these 

variables (biomass) was analyzed (when possible), rather than analyzing them separately. For 

other acceptable chronic and related (e.g., 28-day juvenile or adult) tests, the toxicological 

endpoints analyzed were survival, reproduction, hatchability, or growth as appropriate.

Regression analysis was used, both to demonstrate that a concentration-effect relationship 

was present, and to estimate chronic values at a consistent level of effect. Estimates of effect 

concentrations can generally be made with precision for a 50 percent reduction in response 

(EC50), but at low percent reductions such precision is decreased. A major reduction, such as 50 

percent, is not consistent with the intent of establishing chronic criteria to protect the population 

from long-term effects. In contrast, a concentration that causes a low level of reduction in 

response, such as an EC5 or EC10, is rarely statistically significantly different from the control 

treatment. EPA selected EC20 values to be used to estimate a low level of effect that would be 

statistically different from control effects, yet not so severe as to be expected to cause chronic 

impacts at the population level (see U.S. EPA 1999). For calculation of the chronic criterion, the 

EC20 point estimate was selected for use over a NOEC or LOEC as the measure of effect to use, 

as NOECs and LOECs are highly dependent on test concentrations selected. Furthermore, point 

estimates provide additional information that is difficult to determine using NOEC and LOEC 
13

effect measures, such as a measure of effect level across the range of tested concentrations, and 

the confidence intervals around those measures of effect.

The typical assessment endpoints for aquatic life criteria are based on unacceptable 

effects on growth, reproduction, or survival of the assessed taxa. These measures of effect on 

toxicological endpoints of consequence to populations are provided by results from the acute and 

chronic toxicity tests with aquatic plants and animals. The toxicity values (i.e., measures of 

effect expressed as genus means) are used in the genus sensitivity distribution of the aquatic 

community to derive the aquatic life criteria. Endpoints used in this assessment are listed in 

Table 1.

Table 1. Summary of Assessment Endpoints and Measures of Effect Used in Criteria 

Derivation for Ammonia.

Assessment Endpoints for the Aquatic 

Community

Measures of Effect

Survival, growth, and reproduction of 

freshwater fish, other freshwater vertebrates,

and invertebrates

For acute effects: LC50 or EC50

For chronic effects: EC20, NOEC and LOEC, 

calculated MATC

Maintenance and growth of aquatic plants

from standing crop or biomass

Not relevant for ammonia because plants are 

substantially less sensitive than animals

MATC = maximum acceptable toxicant concentration (geometric mean of NOEC and LOEC)

NOEC = No observed effect concentration

LOEC = Lowest observed effect concentration

LC50 = Lethal concentration to 50% of the test population

EC50/EC20 = Effect concentration to 50/20% of the test population

Chronic averaging period of 30 days

The 30-day averaging period for chronic effects has been retained from the 1999 chronic 

criterion, as is the restriction that the highest 4-day average within the 30 days may be no greater 

than 2.5 times the chronic concentration (CCC) more than once every three years on average. 

This is based on analysis of chronic data from fathead minnow laboratory tests of different

exposure durations and starting with different age test organisms as summarized below and 

described in greater detail in the 1999 ammonia criteria update.

The 1985 ammonia criteria document specified a CCC averaging period of 4 days as 

recommended in the 1985 Guidelines (Stephan et al. 1985), except that an averaging period of 30 

days could be used when exposure concentrations were shown to have "limited variability". For 
14

ammonia, the toxicity data on the fathead minnow demonstrate how long the averaging period 

should be when concentrations have limited variability, and what restriction applies in terms of 

the maximum concentration that can be reached and for how long within that averaging period. 

Based on 7-day tests, EC20s of 29.34 and 24.88 mg TAN/L were calculated from the data of 

Willingham (1987), adjusted to pH 7. Chronic values of 20.32 mg TAN/L at pH 7 and 20.99 mg 

TAN/L similarly adjusted to pH 7 were reported by Camp Dresser and McKee (1997). The 

geometric mean of the four values is 23.62 mg TAN/L. This is approximately 2.5 times the 

geometric mean EC20 (i.e., 9.396 mg TAN/L at pH 7) for the 30-day early life-stage tests 

conducted on the same species by Swigert and Spacie (1983) and Mayes et al. (1986), [see also 

Appendix B]. 

Thus, in the 1999 criteria document, EPA determined that because the mean chronic 

value from the shorter 7-day toxicity tests with slightly older (< 1 day old) fish is substantially 

higher than the mean chronic value from the longer 30-day ELS tests initiated with newly 

fertilized embryos, the CCC averaging period under this “limited variability” can be 30 days, as 

long as excursions above the CCC are restricted sufficiently to not exceed the mean chronic 

value from the 7-day tests. As indicated in the 1999 AWQC document, a more rigorous 

definition of this excursion restriction is not possible with the data available, especially because 

the information is not available concerning the effects to fish or other animals of variations in 

ammonia concentration within a 7-day test period. It is useful, however, to base the excursion 

restriction on a 4-day period, because this period is the default that already has to be considered 

in calculations of water quality-based effluent limits, and because it provides a substantial 

limitation of variability relative to the 7-day chronic values. While it may be uncertain how 

much higher than the CCC the 4-day average can be, based on the fathead minnow test results

summarized above, 2.5 -fold higher concentrations should be acceptable. Other data and 

justification supporting the use of a longer averaging period for ammonia and the excursion 

restriction is provided in the 1999 AWQC document under Chronic Averaging Period (page 81).

Ammonia toxicity data fulfilling minimum data requirements

Table 2 provides a summary of the number of toxicity data currently available for genera

and species that fulfill the 1985 Guidelines minimum requirements for calculation of acute and 

chronic criteria for freshwater species exposed to ammonia. 
15

Table 2. 1985 Guidelines Minimum Data Requirements Summary Table Reflecting the 

Number of Species and Genus Level Mean Values Represented in the Acute and Chronic 

Toxicity Datasets for Ammonia in Freshwater.

Genus Mean 

Acute Value

(GMAV)

Species Mean 

Acute Value

(SMAV)

Genus Mean 

Chronic Value

(GMCV)

Species Mean 

Chronic Value

(SMCV)

Freshwater

Family Salmonidae in the 

class Osteichthyes

4 11 1 3

Second family in the class 

Osteichthyes, preferably a 

commercially or 

recreationally important 

warmwater species

22 33 6 7

Third family in the phylum 

Chordata (may be in the class 

Osteichthyes or may be an 

amphibian, etc.)

3 4 1 1

Planktonic Crustacean 4 6 2 3

Benthic Crustacean 6 8 1 1

Insect 9 11 1 1

Family in a phylum other than 

Arthropoda or Chordata (e.g., 

Rotifera, Annelida, or 

Mollusca)

17 23 4 5

Family in any order of insect 

or any phylum not already 

represented

4 4 1

a

1

a

Total 69 100 17 22

a

In the absence of other chronic data to fulfill this MDR for another phylum not already represented in the chronic 

dataset, the acute data for species within the phylum Annelida were used to calculate a surrogate chronic value, by 

applying a geometric mean ACR from the available invertebrate ACRs. 

Since the data available regarding the toxicity of ammonia to freshwater phytoplankton 

and vascular plants reported in the 1985 AWQC document indicate that aquatic plants appear to 

be two orders of magnitude less sensitive than the aquatic animals tested, it is assumed that any 

ammonia criterion appropriate for the protection of freshwater aquatic animals will also be 

protective of aquatic vegetation (U.S. EPA 1985, 1999, 2009). The greater tolerance of these 

taxa to ammonia is due in part to the fact that ammonia is a readily available and energy-efficient 

source of nitrogen for plants; although ammonia can be toxic when present at high 

concentrations. For example, the experimental data concerning the toxicity of ammonia to 
16

freshwater phytoplankton show negative effects occurring in the green alga, Scenedesmus 

obliquus, ranging from approximately 26.88 to 70.14 mg TAN/L with regards to oxygen

evolution and reduction in carbon dioxide photoassimilation (Abeliovich and Azov 1976). 

Additionally, ammonia caused growth inhibition and cell death of the green alga, Chlorella 

vulgaris, at concentrations ranging from 326 to 1,330 mg TAN/L (Przytocka-Jusiak 1976); and 

for another algal species, Ochromonas sociabilis, a concentration of 256 mg TAN/L was 

algicidal while a concentration of approximately half that (128 mg TAN/L) reduced population 

development (assuming pH 6.5 and 30 ̊C; see Bretthauer 1978). Furthermore, Champ et al. 

(1973) investigated the effects of treating a Texas pond with a mean ammonia concentration of 

25.6 mg/L NH3 (unionized ammonia) for two weeks. A diverse population of dinoflagellates, 

diatoms, desmids, and blue-green algae had been reduced by 95% at the end of the experiment. 

At the same time, the pond was virtually eradicated of all rooted aquatic vegetation. Compared 

to the 2013 chronic criterion magnitude of 1.9 mg TAN/L, the results from these plant tests, 

which are considered as chronic effects according to the 1985 Guidelines, indicate that the 2013 

CCC for ammonia will be protective of aquatic plants.

Much of the early work concerning the response of freshwater vegetation to high 

ammonia concentrations is not quantitative or the result of research exploring the possible use of 

ammonia as an aquatic herbicide (U.S. EPA 1985). There is no new evidence to suggest that 

freshwater phytoplankton and vascular species are more sensitive to ammonia than invertebrates 

or fish. Until such a time as those data are produced, EPA will continue to assume that any 

ammonia criterion appropriate for the protection of freshwater aquatic animals will also be 

protective of aquatic vegetation.

Conceptual Model

A conceptual model consists of a written description and diagram (U.S. EPA 1998) that 

illustrates the relationships between human activities, stressors, and ecological effects on 

assessment endpoints. The conceptual model links exposure characteristics with the ecological 

endpoints important for management goals. Under the CWA, these management goals are 

established by states and tribes as designated uses of waters of the United States (for example, 

aquatic life support). In deriving aquatic life criteria, EPA is developing acceptable thresholds 
17

for pollutants that, if not exceeded, are expected to protect designated uses. A state and/or tribe 

may implement these criteria by adopting them into their respective water quality standards.

Conceptual diagram

Environmental exposure to ammonia, while ultimately determined by various site 

specific conditions and processes, occurs from human activities related to agricultural practices, 

urbanization and industrial processes, or from natural sources. Point and non-point sources 

contribute to elevated concentrations in ambient surface water. The environmental fate 

properties of ammonia indicate that direct discharge, runoff, groundwater transport, and 

atmospheric deposition represent the pathways of greatest transport to the ambient surface waters 

which serve as habitat for aquatic organisms. These sources and transport mechanisms are 

depicted in the conceptual model below (Figure 2). The model also depicts exposure pathways 

for biological receptors of concern (e.g., aquatic animals) and the potential attribute changes (i.e., 

effects such as reduced survival, growth and reproduction) in the ecological receptors due to 

ammonia exposure.

The conceptual model provides a broad overview of how aquatic organisms can 

potentially be exposed to ammonia. Transport mechanisms and exposure pathways are not 

quantitatively considered in the derivation of aquatic life criteria, which are effects assessments, 

not risk assessments. Derivation of criteria focuses on effects on survival, growth and 

reproduction of aquatic organisms. However, the pathways, receptors, and attribute changes 

depicted in Figure 2 may be helpful for states and tribes as they adopt criteria into standards and 

need to evaluate potential exposure pathways affecting designated uses.
18

Figure 2: Conceptual Model for Ammonia Effects on Aquatic Animals.

(Available at: http://www.epa.gov/caddis/ssr_amm_int.html)
19

Analysis Plan

During development of CWA section 304(a) criteria, EPA assembles all available 

toxicity test data and considers which data are relevant that also meet data quality acceptance

standards for all genera. Where data allow, two to four criterion values are developed (acute and

chronic freshwater, acute and chronic saltwater). If plants are the most sensitive relative to 

vertebrates and invertebrates, plant criteria are developed. This criteria update document is 

specific to ammonia in fresh water, and thus, only two criterion values (freshwater acute and 

chronic) are derived in this document. Available data indicate freshwater plants are not more 

sensitive to ammonia than freshwater animals, thus, plant criteria are not developed. Finally,

ammonia does not bioaccumulate in aquatic animals, thus, final tissue values are not developed.

These criteria are based on a sensitivity distribution (SD) comprised of ranked genus 

mean acute values (GMAVs), calculated from combined species mean acute values (SMAVs

within each genus) for acceptable data. SMAVs are calculated using the geometric mean for all 

acceptable measures of effect based on the results of toxicity tests within a given species (e.g., all 

EC50s from acceptable acute tests for Daphnia magna). GMAVs are then calculated using the 

geometric means of all SMAVs within a given genus (e.g., all SMAVs for genus Daphnia, such 

as Daphnia pulex, Daphnia magna). If only one SMAV is available for a genus, then the 

GMAV is represented by that value. GMAVs are then rank-ordered by sensitivity from most 

sensitive to least sensitive. The final acute value (FAV) is determined by regression analysis 

using a log-triangular fit based on the four most sensitive genera (reflected as GMAVs) in the 

data set to interpolate or extrapolate (as appropriate) to the 5th percentile of the distribution 

represented by the tested genera. If there are 59 or more GMAVs, as is the case with ammonia, 

the four GMAVs closest to the 5th percentile of the distribution are used to calculate the FAV.

The acute criterion magnitude is the FAV divided by two, in order to provide an acute criterion

magnitude protective of nearly all individuals in 95% of all genera, since the effect endpoint is a 

50th percentile effect (e.g., LC50 or EC50) (see 1985 Guidelines, Section XI. Criterion, B.).

Although the aquatic life criteria derivation process relies on selected toxicity endpoints 

from the sensitive species tested, it does not necessarily mean that the selected toxicity endpoints 

reflect the sensitivity of the most sensitive species existing in a given environment. The intent of 

the eight minimum data requirements is to serve as a sample representative of the aquatic 

community. These minimum data requirements represent different ecological, trophic, 
20

taxonomic and functional differences observed in the natural aquatic ecosystem. The use of the 

four most sensitive genera to determine the final criterion value is a censored statistical approach 

than improves estimation of the lower tail (most sensitive) of the distribution when the shape of 

the overall distribution, particularly in the less sensitive part of the distribution, is uncertain.

The chronic criterion may be determined by one of two methods. If all eight minimum data 

requirements are met with acceptable chronic test data (as is the case with ammonia), then the 

chronic criterion is derived using the same method used for the acute criterion. Genus Mean 

Chronic Values (GMCVs) are derived from available Species Mean Chronic Values (SMCVs)

and are then rank-ordered from least to most sensitive, and the Final Chronic Value (FCV) is 

calculated based on regression analysis of a censored distribution using the four most sensitive 

GMCVs, similar to calculation of the FAV. Unlike the FAV, however, the FCV directly serves 

as the basis for the chronic criterion without further adjustment because the endpoint measured 

represents a low level (e.g., EC20 or NOEC) of effect (see 1985 Guidelines).

In addition, whenever adequately justified, a state can develop a site-specific criterion in 

lieu of the use of a national recommended criterion (U.S. EPA 1983). The site-specific criterion 

may include not only site-specific criterion concentrations, but also site-specific durations or

averaging periods, site-specific frequencies of allowed excursions, and representative species 

present at a given site, where supported by sound science (U.S. EPA 1991). The Revised 

Deletion Process for the Site-Specific Recalculation Procedure for Aquatic Life Criteria (U.S.

EPA 2013) provides guidance on revising the taxonomic composition of the toxicity data set 

used for the sensitivity distribution upon which a site-specific criterion is based, in order to better 

reflect the assemblage of organisms that resides at the site. For more information on criteria 

derivation, see: 

http://water.epa.gov/scitech/swguidance/waterquality/standards/upload/2009_01_13_criteria_8

5guidelines.pdf.

The criteria presented are the Agency’s best estimate of maximum ambient 

concentrations of ammonia to protect most freshwater aquatic organisms from unacceptable 

short- or long-term effects. Results of intermediate calculations such as Species Mean Acute 

Values (see in Appendix A) and chronic values (see in Appendix B) are specified to four 

significant figures to prevent rounding error in subsequent calculations, not to reflect the 

precision of the value. All of the ammonia acute values (LC50s and EC50s) in Appendix A of this 
21

document were converted to TAN acute values using the reported temperatures and pHs as 

described using an example in Appendix D (Conversion of Acute Results of Toxicity Tests). 

Similarly, all of the ammonia chronic values (EC20s) in Appendix B were converted to TAN 

chronic values as described in Appendix E (Conversion of Chronic Results of Toxicity Tests).

EFFECTS ANALYSES FOR FRESHWATER AQUATIC ORGANISMS

The acute and chronic ammonia toxicity data used here to update the acute and chronic 

criteria for ammonia (freshwater) were collected via literature searches of EPA’s ECOTOX 

database, EPA’s Ambient Aquatic Life Water Quality Criteria for Ammonia (U.S. EPA 1985, 

1998, 1999), data provided by the U.S. Fish and Wildlife Service and the National Oceanic and 

Atmospheric Administration (NOAA) National Marine Fisheries Service (collectively known as 

the Services), and EPA regional and field offices. Relevant papers were identified, by title and 

abstract, and their data screened according to data quality criteria described in the 1985 

Guidelines. All available, reliable acute and chronic toxicity values published since 1985 were 

incorporated into the appropriate ammonia AWQC tables and used to recalculate the CMC and 

the CCC, as outlined in detail in the 1985 Guidelines. The most recent literature search covered 

the period from 1985 through October 2012.

Acute Toxicity to Aquatic Animals

All available data relating to the acute effects of ammonia on aquatic animals were 

considered in deriving the ammonia criteria and were subjected to a data quality review per the 

1985 Guidelines. The acute effects concentrations are all normalized to pH 7.0 (for all 

organisms) and temperature 20°C (for invertebrates) as indicated via the equations provided in 

Appendix D. The pH and temperature conditions to which these data are normalized were

deemed to be generally representative of ambient surface water. Data that were suitable for the 

derivation of a freshwater FAV are presented in Appendix A.

The GMAVs ranked according to sensitivity, as well as the new (2013) and previous 

(1999) acute criterion values (CMCs), are shown in Figure 3. The GMAVs represent LC50s or 

EC50s, whereas the CMC (the FAV/2) values represent concentrations that are expected to be
22

lethal to less than 50% of the individuals in either the fifth percentile genus, or, a sensitive 

commercially or recreationally important species (e.g., adult rainbow trout).

For this 2013 AWQC document, results from acute toxicity tests that met test 

acceptability and quality (according to the 1985 Guidelines) were available for 44 species of fish, 

52 species of invertebrates and four species of amphibians. This data includes ammonia toxicity 

test data on 52 new species of aquatic animals not previously included in the 1999 acute criterion 

dataset. There are now 69 genera represented in the freshwater acute toxicity dataset for 

ammonia, and of the 69 genera (represented in Appendix A and listed according to sensitivity in 

Table 3), approximately half are invertebrates. The acute dataset more than fulfills the eight 

minimum data requirements outlined in the 1985 Guidelines with between three and 22 genera 

represented for each taxa category specified (see Table 2 above). The acute criterion dataset now 

includes 12 species of aquatic animals Federally-listed as threatened, endangered or species of 

concern. Freshwater invertebrates in the Phylum Mollusca, particularly freshwater mussels in 

the family Unionidae, freshwater clams, and some non-pulmonate snails, are the predominant 

group of aquatic organisms ranked in the lowest quartile. The four most acutely sensitive genera 

are all freshwater bivalve mussels (Table 3). GMAVs for freshwater mollusks in general, are 

now among the most influential in the 2013 acute criterion dataset.

Data for glochidia and juvenile life stages of freshwater unionid mussels were evaluated 

for acceptability based on the 1985 Guidelines, the approved ASTM protocol for toxicity testing 

with these life stages of unionid mussels (ASTM 2006), and recent studies on the most 

ecologically relevant toxicological endpoint(s) and exposure duration(s) for glochidia tests by 

Bringolf et al. (2013). The acute unionid mussel dataset for ammonia now includes acceptable 

data for 11 genera, totaling 16 species of freshwater mussels, as well as two sensitive species of 

non-pulmonate snails. Of these, four of the 18 mollusk species included in 2013 acute dataset 

are Federally-listed as threatened or endangered (as identified in Table 3). 

Nearly all states in the continental United States have freshwater unionid mussel fauna in 

at least some of their waters (Abell et al. 2000; Williams et al. 1993; Williams and Neves 1995). 

While the number of freshwater unionid mussel species is less and the distribution is sparse in 

the dry western states, even New Mexico and Arizona have at least one native mussel species 

(Williams et al. 1993). Moreover, approximately one-quarter of nearly 300 freshwater unionid 

mussel taxa in the USA are Federally-listed as endangered, threatened or of special concern. In 
23

addition, non-pulmonate snails are relatively ubiquitous compared to mussels and of the 650

freshwater snail species, 25 species are Federally-listed. Every state in the continental U.S. has 

at least one family of non-pulmonate snail in at least some of their waters. Thus, considering 

that freshwater unionid mussels are among some of the most sensitive genera in the dataset, and 

that all states have at least one freshwater unionid mussel or bivalve mollusk, or non-pulmonate 

snail species, another relatively sensitive mollusk group, native or present in at least some of 

their waters, EPA is recommending a single national acute criterion to be applied to all waters

rather than different criteria based on the presence or absence of mussels. 

The most sensitive fish SMAV is for mountain whitefish, Prosopium williamsoni (SMAV

of 51.93 mg TAN/L), representing one of the four genera of salmonids in the acute dataset, 

followed by the second most sensitive fish, the Lost River sucker (SMAV of 56.62 mg TAN/L), 

which is an endangered species (Table 3). The mountain whitefish GMAV is ranked eighth most 

sensitive after seven more sensitive GMAVs for freshwater mussel species, thus, salmonids 

should be adequately protected by the new acute criterion. The next most sensitive salmonid 

genus is Oncorhynchus, represented by data for six different species, three of which are 

threatened or endangered, with SMAVs ranging from 78.92 mg TAN/L for Cutthroat trout, O. 

clarkii, to 180.7 mg TAN/L for pink salmon, O. gorbuscha. The GMAV for Oncorhynchus 

(99.15 mg TAN/L) is ranked #25 in acute sensitivity rank at pH 7 and temperature 20°C (Table 

3).

The four lowest GMAVs in this 2013 ammonia AWQC update are for invertebrate 

species (specifically, freshwater bivalve mollusks dominated by mussels in the family 

Unionidae). Because the most sensitive GMAVs are all represented by invertebrate species, the 

CMC is both pH-dependent, in accordance with the acute pH-toxicity relationship for all aquatic 

organisms, and temperature-dependent, due to the invertebrate acute-temperature relationship.
24

Figure 3. Ranked Freshwater Genus Mean Acute Values (GMAVs) with Criterion 

Maximum Concentrations (CMCs).

Summaries of studies used in acute criterion determination

Presented in this section are brief summaries of the results of acute toxicity tests that 

meet the data quality acceptability criteria and that are used directly for deriving the FAV (i.e., 

serve as the basis for the SMAV or GMAV of one of the most sensitive genera). As per the 1985 

Guidelines, whenever there are 59 or more GMAVs in the acute criteria dataset, the FAV is 

calculated using the four GMAVs closest to the 5th percentile of the distribution. 

The four species and associated endpoints (SMAV or GMAV) used in calculating the 

acute criterion (sensitivity rank 2-5) are ranked below from most to least sensitive:

1

1 0

100

1000

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

GMAV (mg TAN/L) at pH 7 (and 20 ̊C invertebrates)

Genus Mean Acute Values

(Cumulative Fraction)

Summary of Ranked Ammonia GMAVs

Freshwater

Freshwater Unionid Mussels

Other Freshwater Mollusks

Other Freshwater Invertebrates

Freshwater Fish

Freshwater Amphibians

2013 CMC = 17 mg TAN/L

1999 CMC (salmonids present) = 24 mg TAN/L
25

2. Lasmigona subviridis, Green Floater (GMAV= 23.41 mg TAN/L)

3. Epioblasma capsaeformis, Oyster mussel (GMAV= 31.14 mg TAN/L)

4. Villosa iris, Rainbow Mussel (GMAV= 34.23 mg TAN/L)

5. Lampsilis sp. (GMAV=46.63 mg TAN/L)

The most sensitive species Venustaconcha ellipsiformis (SMAV=23.12 mg TAN/L) is not 

included in the criteria numeric calculation, because it falls below the 5th percentile in sensitivity 

in the distribution of 69 genera included in the dataset.

Summaries are provided on the basis of individual species or genera (in cases where more 

than one species is included in the calculation of the GMAV). All values are provided in terms 

of total ammonia nitrogen (TAN), either as reported by the authors or as converted from the 

reported values for unionized ammonia, pH, and temperature (using the speciation relationship) 

applied in the 1999 AWQC document (i.e., Emerson et al. 1975). In the special cases where the 

result of a test is considered an upper limit on an acute value, the value is ascribed a greater than 

(“>”) sign indicating as much. 

Lasmigona subviridis (green floater)

The GMAV/SMAV for the green floater, a freshwater bivalve mollusk, of 23.41 mg 

TAN/L is based on the geometric mean of three 96-hr EC50s from tests using less than twomonth old juveniles as reported in Black (2001). Test solutions were renewed after 48 hours. 

The mean pH and test temperature for two of the tests was 7.73 and 24°C, and for the third, 7.92 

and 24.8°C. Control survival exceeded 90 percent in all three tests. The reported EC50s at test 

temperature and pH expressed on the basis of TAN were 6.613, 6.613 and 3.969 mg TAN/L, 

respectively. Adjusted to pH 7 and 20°C, the EC50s are 24.24, 24.24 and 21.84 mg TAN/L, 

respectively (Appendix A). The GMAV for juvenile green floaters of 23.41 mg TAN/L

represents the second lowest in the acute dataset, and the lowest of the four GMAVs used to 

calculate the FAV (Table 3).

Epioblasma capsaeformis (oyster mussel)

The GMAV/SMAV for the endangered oyster mussel (31.14 mg TAN/L) is the third 

lowest in the acute dataset (Table 3), and is based on the geometric mean of a 96-hr EC50 from a 
26

renewal test using less than five-day old juveniles, and two 6-hr EC50s from static tests 

conducted with two-hour old glochidia (Wang et al. 2007b). The mean pH and test temperature 

for all three tests was 8.5 and 20°C. Control survival exceeded 90 percent in all tests. The 

estimated measured EC50 for juvenile oyster mussels at test temperature and pH was 4.760 mg 

TAN/L, after adjusting the reported nominal EC50 by multiplying by a factor of 0.835 (i.e., 

measured total ammonia concentrations were 83.5 percent of nominal concentrations for 96 hour 

juvenile exposures). The reported EC50s for glochidia were 3.4 and 5.0 mg TAN/L, respectively 

(no further adjustment necessary). These EC50s normalized to pH 7 and 20°C are 53.63, 17.81 

and 31.61 mg TAN/L, for the two glochidia and juveniles respectively (Appendix A).

Villosa iris (rainbow mussel)

Ten EC50s from several studies (Goudreau et al. 1993; Scheller 1997; Mummert et al. 

2003; Wang et al. 2007b) using two different life stages (glochidia and juvenile) and range of 

ages within each life-stage were used to calculate the GMAV/SMAV for rainbow mussel 

(Appendix A). All tests were either static or static renewal where concentrations were measured. 

The GMAV of 34.23 mg TAN/L is the fourth lowest in the acute dataset (Table 3), and is 

composed of individual EC50 values (expressed as TAN and normalized to pH 7 and 20°C) 

ranging from 12.62 to 99.28 mg TAN/L (Appendix A). The difference in pH and test 

temperature among the 10 different tests ranged from 7.29 to 8.40 and 12.6 to 25.0°C, 

respectively. Control survival exceeded 90 percent in all tests regardless of life-stage tested. 

The glochidia were not substantially more sensitive than the juveniles (less than a factor of 2 

difference).

Mussels in Genus Lampsilis

Freshwater unionid mussels within the Genus Lampsilis represent the most widely tested 

genus to date. The GMAV of 46.63 mg TAN/L reflects the geometric mean of SMAVs for six 

species, two (Lampsilis abrupta and L. higginsii) which are endangered and a third (L. 

rafinesqueana) that is a Federal species of concern (Table 3). The SMAVs for this genus range 

from 26.03 mg TAN/L (L. abrupta) to 69.97 mg TAN/L (L. rafinesqueana), and are composed 

of anywhere from one (L. abrupta) to fourteen (L. siliquoidea) individual EC50s (Appendix A). 

The range of EC50s used to calculate the FAV, normalized to pH 7 and 20°C across all species of 
27

Lampsilis is from 24.30 to 160.5 mg TAN/L (see Appendix A). The GMAV for Lampsilis is the 

fifth most sensitive in the acute dataset, and the highest of the four GMAVs used to calculate the 

FAV (Table 3). Both glochidia and juvenile data were available for three of the six Lampsilis

species, showing an inconsistent pattern of relative sensitivity. 

Table 3. Ranked Genus Mean Acute Values.

Table 3. Ranked Genus Mean Acute Values

Rank

GMAV

(mg TAN/L) Species

SMAV

(mg TAN/L)

69 2515 Insect,

Erythromma najas 2515

68 994.5 Caddisfly,

Philarctus quaeris 994.5

67 735.9 Beetle,

Stenelmis sexlineata 735.9

66 686.2

Crayfish,

Orconectes immunis 1550

Crayfish,

Orconectes nais 303.8

65 681.8

Midge,

Chironomus riparius 1029

Midge,

Chironomus tentans 451.8

64 442.4 Mayfly,

Drunella grandis 442.4

63 387.0 Aquatic sowbug,

Caecidotea racovitzai 387.0

62 378.2 Isopod,

Asellus aquaticus 378.2

61 281.5 Threespine stickleback,

Gasterosteus aculeatus 281.5

60 246.5

Mayfly,

Callibaetis skokianus 364.6

Mayfly,

Callibaetis sp.

166.7

59 233.0 Dragonfly,

Pachydiplax longipennis 233.0

58 222.2 Mottled sculpin,

Cottus bairdii 222.2

57 219.3 Western mosquitofish,

Gambusia affinis 219.3

56 218.7 Oligochaete worm,

Lumbriculus variegatus 218.7

55 216.5 Tubificid worm,

Tubifex tubifex 216.5

54 211.6 Marsh ramshorn snail,

Planorbella trivolvis 211.6
28

Table 3. Ranked Genus Mean Acute Values

Rank

GMAV

(mg TAN/L) Species

SMAV

(mg TAN/L)

53 192.6 Scud,

Hyalella azteca 192.6

52 192.4 Stonefly,

Skwala americana 192.4

51 185.2 Mozambique tilapia,

Oreochromis mossambicus 185.2

50 181.8

Amphipod,

Crangonyx pseudogracilis 270.5

Amphipod,

Crangonyx sp.

122.2

49 170.2 Tubificid worm,

Limnodrilus hoffmeisteri 170.2

48 164.5 Pouch snail,

Physa gyrina 164.5

47 164.0 Damselfly,

Enallagma sp.

164.0

46 162.6 Water flea,

Chydorus sphaericus 162.6

45 159.2 Fathead minnow,

Pimephales promelas 159.2

44 157.8

Brook trout,

Salvelinus fontinalis 156.3

Lake trout,

Salvelinus namaycush 159.3

43 156.7 Shortnose sturgeon,

Acipenser brevirostrum (LS) 156.7

42 146.5

White sucker,

Catostomus commersonii 157.5

Mountain sucker,

Catostomus platyrhynchus 136.2

41 143.9

Water flea,

Ceriodaphnia acanthine 154.3

Water flea,

Ceriodaphnia dubia 134.2

40 142.9 Water flea,

Simocephalus vetulus 142.9

39 142.4 Channel catfish,

Ictalurus punctatus 142.4

38 138.0 Red swamp crayfish,

Procambarus clarkii 138.0

37 136.7

Atlantic salmon,

Salmo salar (LS) 183.3

Brown trout,

Salmo trutta 102.0

36 134.8

White perch,

Morone americana 132.7

White bass,

Morone chrysops 144.0
29

Table 3. Ranked Genus Mean Acute Values

Rank

GMAV

(mg TAN/L) Species

SMAV

(mg TAN/L)

Striped bass,

Morone saxatilis 246.2

Sunshine bass,

Morone saxatilis x chrysops 70.22

35 125.0

Water flea,

Daphnia magna 157.7

Water flea,

Daphnia pulicaria 99.03

34 122.5 Clawed toad,

Xenopus laevis 122.5

33 119.5 Flatworm,

Dendrocoelum lacteum 119.5

32 117.1 Walleye,

Sander vitreus 117.1

31 115.9 Central stoneroller,

Campostoma anomalum 115.9

30 110.0

Rainbow dace,

Cyprinella lutrensis 196.1

Spotfin shiner,

Cyprinella spiloptera 83.80

Steelcolor shiner,

Cyprinella whipplei 80.94

29 109.0 Dwarf wedgemussel,

Alasmidonta heterodon (LS) 109.0

28 109.0 Pink papershell,

Potamilus ohiensis 109.0

27 106.9

Green sunfish,

Lepomis cyanellus 150.8

Pumpkinseed,

Lepomis gibbosus 77.53

Bluegill,

Lepomis macrochirus 104.5

26 106.3 Common carp,

Cyprinus carpio 106.3

25 99.15

Golden trout,

Oncorhynchus aguabonita 112.1

Cutthroat trout,

Oncorhynchus clarkii 78.92

Pink salmon,

Oncorhynchus gorbuscha 180.7

Coho salmon,

Oncorhynchus kisutch (LS) 87.05

Rainbow trout,

Oncorhynchus mykiss (LS) 82.88

Chinook salmon,

Oncorhynchus tshawytscha (LS) 82.39

24 96.72 Topeka shiner,

Notropis topeka (LS) 96.72
30

Table 3. Ranked Genus Mean Acute Values

Rank

GMAV

(mg TAN/L) Species

SMAV

(mg TAN/L)

23 96.38 Leopard frog,

Rana pipiens 96.38

22 89.36 Long fingernailclam,

Musculium transversum 89.36

21 89.06

Smallmouth bass,

Micropterus dolomieu 150.6

Largemouth bass,

Micropterus salmoides 86.02

Guadalupe bass,

Micropterus treculii 54.52

20 88.62 Great pond snail,

Lymnaea stagnalis 88.62

19 74.66 Guppy,

Poecilia reticulata 74.66

18 74.25

Johnny darter,

Etheostoma nigrum 71.45

Orangethroat darter,

Etheostoma spectabile 77.17

17 72.55 Rio Grande silvery minnow,

Hybognathus amarus 72.55

16 71.56

Spring peeper,

Pseudacris crucifer 61.18

Pacific tree frog,

Pseudacris regilla 83.71

15 71.25

Mucket,

Actinonaias ligamentina 63.89

Pheasantshell,

Actinonaias pectorosa 79.46

14 70.73 Giant floater mussel,

Pyganodon grandis 70.73

13 69.36 Shortnose sucker,

Chasmistes brevirostris 69.36

12 68.54 Pagoda hornsnail,

Pleurocera uncialis 68.54

11 63.02 Golden shiner,

Notemigonus crysoleucas 63.02

10 62.15 Pebblesnail,

Fluminicola sp.

62.15

9 56.62 Lost River sucker,

Deltistes luxatus(LS) 56.62

8 51.93 Mountain whitefish,

Prosopium williamsoni 51.93

7 47.40 Atlantic pigtoe,

Fusconaia masoni 47.40

6 46.93 Pondshell mussel,

Utterbackia imbecillis 46.93

5 46.63 Pink mucket,

Lampsilis abrupta (LS) 26.03
31

Table 3. Ranked Genus Mean Acute Values

Rank

GMAV

(mg TAN/L) Species

SMAV

(mg TAN/L)

Plain pocketbook,

Lampsilis cardium 50.51

Wavy-rayed lampmussel,

Lampsilis fasciola 48.11

Higgin's eye,

Lampsilis higginsii (LS) 41.90

Neosho mucket,

Lampsilis rafinesqueana (LS) 69.97

Fatmucket,

Lampsilis siliquoidea 55.42

4 34.23 Rainbow mussel,

Villosa iris 34.23

3 31.14 Oyster mussel,

Epioblasma capsaeformis (LS) 31.14

2 23.41 Green floater,

Lasmigona subviridis 23.41

1 23.12 Ellipse,

Venustaconcha ellipsiformis 23.12

FAV = 33.52

CMC = 17

LS = Federally-listed as threatened or endangered species

Chronic Toxicity to Freshwater Aquatic Animals

Freshwater chronic toxicity data that meet the test acceptability and quality 

assurance/control criteria are presented in Appendix B. All tests were conducted with measured 

concentrations of ammonia. Ammonia chronic toxicity data are available for 21 species of 

freshwater organisms: ten invertebrate species (mussels, clam, snail, cladocerans, daphnid, and 

insect) and 11 fish species, including three Federally-listed salmonid species. The chronic 

dataset includes data for three freshwater unionid mussel species, one freshwater non-pulmonate 

snail species, and two fish species not included in the 1999 criteria (see Appendix B). It also 

includes an estimate of chronic effects for the Phylum Annelida, to meet the data requirement of 

a species in “a family in any order of insect or any phylum not already represented,” as described 

below.

Each chronic test was reviewed to determine acceptability based on the dilution water, 

control mortality, experimental design, organism loading, etc., as consistent with ASTM 

standards, including for freshwater mussels via E2455-06 (ASTM 2006). The concentration of 
32

dissolved oxygen was also reviewed to determine acceptability based on the general limits 

specified in the 1999 AWQC document. The mean measured dissolved oxygen concentration 

and the lower limit for dissolved oxygen concentration required to be protective varies based on 

taxa group. The mean dissolved oxygen concentration for toxicity tests should be at least 6.5 

mg/L for salmonids, 6.0 mg/L for invertebrates, and the lower limit of dissolved oxygen should 

be 5.0 mg/L to be protective of both of these groups of organisms (U.S. EPA 1999). 

Based on the determination that the test methodology used was acceptable, the studies

were evaluated to determine whether the ammonia caused a reduction in (a) survival (if over a 

period of at least seven days), (b) growth, or (c) reproduction. If the test demonstrated reduction

in any of these toxicological endpoints, the test could be accepted for use in calculating the 

chronic value (CV).

Acceptable 28-day survival tests using juvenile freshwater mussels and juvenile 

freshwater snails and growth tests using juvenile freshwater snails were evaluated for inclusion 

in the derivation of the chronic aquatic life criterion when the test concentration caused a 

reduction in survival or growth of 20 percent or more of these types of organisms at those life 

stages. Based on evaluation of the individual studies (Wang et al. 2007a; Wang et al. 2011), 

growth data for juvenile mussels was not used in the derivation of the chronic criterion due to 

uncertainty in method of measurement for the growth endpoint (see Effects Characterization for 

further discussion). 

All chronic data in individual studies were analyzed using regression analysis to 

demonstrate the presence of a concentration-effect relationship within the test. For those studies 

that demonstrated a concentration-effect relationship, EPA used regression analysis to estimate 

the EC20.

Sixteen GMCVs are presented in Appendix B and ranked according to sensitivity in 

Table 4. The four lowest values were used to calculate the FCV, because values for fewer than 

59 genera exist. EPA calculated the chronic criterion based on fifth percentile of the GMCVs in 

Table 4. The GMCVs for the four most sensitive species are ranked below from most to least

sensitive:

1. Lampsilis spp, Wavy-rayed lamp mussel and Fatmucket (GMCV=2.126 mg TAN/L)

2. Villosa iris, Rainbow mussel (GMCV= 3.501 mg TAN/L)
33

3. Lepomis spp., Bluegill and Green sunfish (GMCV= 6.920 mg TAN/L)

4. Musculium transversum, Long fingernailclam (GMCV= 7.547 mg TAN/L)

The chronic criterion magnitude is 1.9 mg TAN/L at 20°C and pH 7. The four most 

sensitive species are predominantly mollusks although Lepomis species (bluegill and green 

sunfish) comprise the third most sensitive GMCV. Figure 4 shows the GMCVs ranked 

according to sensitivity and shows the 2013 chronic criteria magnitude as well as the 1999 

criterion value (based on fish early life stages) for comparative purposes.

Figure 4. Ranked Freshwater Genus Mean Chronic Values (GMCVs) with Criterion 

Continuous Concentrations (CCCs).

0

1

1 0

100

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

GMCV (mg TAN/L) at pH 7 (and 20 ̊C invertebrates)

Genus Mean Chronic Values

(Cumulative Fraction)

Summary of Ranked Ammonia GMCVs

Freshwater

Freshwater Unionid Mussels

Other Freshwater Mollusks

Other Freshwater Invertebrates

Freshwater Fish

2013 CCC = 1.9 mg TAN/L

1999 CCC = 4.5 mg TAN/L
34

Summaries of studies used in chronic criterion determination

The following presents a species-by-species discussion of freshwater chronic data used in 

deriving the chronic criterion magnitude for ammonia. All analyses were conducted in terms of 

TAN, either as reported by the authors or as converted from the reported values for unionized

ammonia, pH, and temperature (using the speciation relationship in Emerson et al. 1975). EC20

values were adjusted to pH 7, and for invertebrates, also adjusted to a temperature of 20°C. 

SMCVs were used when data were available for only one species. When data for more than one 

species in a taxon were available, GMCVs were calculated from the SMCVs. All of the CVs 

(EC20 values), SMCVs, and GMCVs derived are tabulated and included in Appendix B. For 

some of the new chronic data, authors reported EC20 values on the basis of TAN. In such cases 

these reported CVs were normalized to pH 7 and 20°C (temperature normalization for 

invertebrates only), and utilized for the analysis. The results of all intermediate calculations such 

as ECs, SMCVs and GMCVs are given to four significant figures to prevent round-off error in 

subsequent calculations, not to reflect the precision of the value. 

Lampsilis species

Lampsilis fasciola (wavy-rayed lampmussel)

Wang et al. (2007a) published results of the effect of ammonia on survival and growth of 

2-month old juvenile freshwater unionid mussels. The 28-day juvenile test was part of a series 

of studies designed to refine the methods for conducting acute and chronic toxicity tests with 

early life stages of freshwater mussels. Dissolved oxygen was maintained above 7.0 mg/L 

during the 28-day test. Survival in the control treatment and lowest ammonia test concentration 

(0.13 mg TAN/L) were 100 and 83 percent, respectively. Survival decreased to 30 percent at 

1.02 mg TAN/L, and zero at 1.98 mg TAN/L. There was no concentration-response relationship 

for either length at 28 days or change in length after 28 days. Using EPA’s TRAP model (see 

Appendix G), the survival EC20 for this freshwater unionid mussel species is 0.4272 mg TAN/L

at test temperature (20°C) and pH (8.2), or 1.408 mg TAN/L when adjusted to pH 7 and 20°C

(Appendix B).
35

Lampsilis siliquoidea (fatmucket)

In a recent study, Wang et al. (2011) evaluated the influence of substrate on the 

sensitivity of two-month-old juvenile mussels to ammonia in 28-day water-only exposure and

substrate exposure. The methods used were similar to those in an earlier study (Wang et al. 

2007a) except for how the organisms were exposed. In this study, the organisms were housed in 

a glass tube with a screen bottom that was suspended in a beaker. The authors conducted two 

exposure conditions simultaneously for comparison of the water-only and substrate exposure. 

The organisms used in the water-only exposure were simply placed on the screen at the bottom

of the tube. The substrate treatment involved substrate that was screened, eliminating both large 

and small particles, with only particles between 300-500 microns retained, which is essentially 

the grain size of medium sand. A layer of substrate was placed on the screen and the organisms 

were placed on top of the relatively inert substrate. In the substrate treatment, the water actively 

flowed past the organisms and through the substrate. Water chemistry was characterized before 

and after passing through the substrate and found not to be substantially altered. Furthermore,

the pH was maintained consistently at approximately pH 8.25 in overlying water and porewater.

The survival response between the water-only and substrate treatments was similar with a 

reported LOEC of 0.53 mg TAN/L in the water-only and 0.88 mg TAN/L for the substrate 

treatment at the test pH 8.25 and temperature 20°C. Mean control survival in both the wateronly and substrate treatments was 95% at the end of the 28-day exposures, which met

acceptability requirements. Dry weight measurements of the mussels increased by 165% in the 

water-only exposure compared to 590% increase in the substrate exposure suggesting that the 

presence of the substrate increased food availability, as noted by the authors. 

Using TRAP threshold sigmoid regression of the survival response results in an EC20 of 

0.5957 mg TAN/L for the water-only and EC20 0.8988 mg TAN/L for the substrate exposure at 

the test pH and temperature, or adjusted to pH 7 and 20°C, chronic values equivalent to 2.128 

and 3.211 mg TAN/L, respectively (Appendix B). Based on the apparent improved health of the 

test organisms in the substrate exposures, and the lack of any significant alteration of water 

chemistry in the exposure, the SMCV 3.211 mg TAN/L, based on survival of juvenile fatmucket 

from the substrate exposures is used to calculate the CCC rather than the water-only exposure.
36

The geometric mean of SMCVs for fatmucket and wavy-rayed lamp mussel of 3.211 and

1.408 mg TAN/L, respectively, results in a GMCV of 2.126 mg TAN/L for the genus Lampsilis

(Table 4).

Villosa iris (rainbow mussel)

The effect of ammonia on survival and growth of this freshwater unionid mussel species 

was also reported in the study by Wang et al. (2007a). Juvenile (2-month-old) rainbow mussels 

were tested via a 28-day test under similar conditions as described above. Survival was ≥ 98 

percent up to the 0.81 mg TAN/L exposure, but fell to 15 percent at 1.67 mg TAN/L and zero 

percent at 3.45 and 7.56 mg TAN/L. EPA’s TRAP was used to generate a chronic value for this 

species based on survival resulting in EC20 of 1.063 mg TAN/L at test temperature (20°C) and 

pH (8.2) – (Appendix G), or 3.501 mg TAN/L adjusted to pH 7.0. Wang et al. (2007a) elected to 

exclude length estimates for concentrations above those where significant survival effects were 

measured (or in this case, 1.67 mg TAN/L). As a result, growth data are available for only three 

effect concentrations, even though there was 15% survival at the 1.67 mg TAN/L treatment 

level. Due to the uncertainties in the limited growth data for this test the growth data was not 

used in the calculation of the GMCV. 

The SMCV and GMCV for this freshwater unionid mussel species is 3.501 mg TAN/L

when adjusted to pH 7 and 20°C (Appendix B).

Lepomis species

Lepomis cyanellus (green sunfish)

Reinbold and Pescitelli (1982a) conducted a 31-day early life-stage (ELS) test that started 

with <24-hour-old embryos. No information was reported concerning the DO concentration, but 

it averaged 70 to 76 percent of saturation (5.7 to 6.2 mg/L) in a similar test in the same report 

with another fish species at about the same temperature. The weight data were not used in the 

calculation of an EC20 because of the greater weight of the fish in test chambers containing fewer 

fish, which indicated that weight was density-dependent. Although overflows resulted in loss of 

fish from some chambers, survival was 96 percent in one of the chambers affected by overflow,

indicating that the survival data were either adjusted or not affected by the overflows. Survival 

by the end of the test was reduced at test concentrations of 6.3 mg TAN/L and above. TRAP 
37

analysis of the survival data resulted in an EC20 of 5.840 mg TAN/L at pH 8.16 and 25.4°C (U.S. 

EPA 1999). Adjusted to pH 7, the EC20 is 18.06 mg TAN/L (Appendix B).

McCormick et al. (1984) conducted a 44-day ELS test starting with <24-hour-old 

embryos. During this test, no effect was found on percent hatch, but survival and growth were 

both reduced at measured test concentrations of 14 mg TAN/L and above. TRAP analysis using 

biomass resulted in an EC20 of 5.61 mg TAN/L at pH 7.9 and 22.0°C for the test (U.S. EPA 

1999). Adjusted to pH 7, the EC20 calculated using the data as previously reported in U.S. EPA 

(1999) is 11.85 mg TAN/L (Appendix B).

The pH-adjusted EC20s of 18.06 mg TAN/L from Reinbold and Pescitelli (1982a) and 

11.85 mg TAN/L from McCormick et al. (1984) agree well with one another. It is possible that 

the second value is lower because it was based on survival and growth, whereas the first value 

was based only on survival. The results of the tests were deemed acceptable for use in 

calculating a SMCV for the species, which is 14.63 mg TAN/L (Table 4) at pH 7. 

Lepomis macrochirus (bluegill)

Similar to the studies summarized above for L. cyanellus, Smith et al. (1984) conducted a 

30-day ELS test starting with <28-hour old embryos of L. macrochirus. No information was 

reported concerning the DO concentration, but the flow-rate was kept high during the test. In 

this study, the authors found no significant reduction in percent hatch up to a test concentration 

of 37 mg TAN/L, but hatched larvae were deformed at this concentration and died within six 

days. By the end of the test, both survival and growth were greatly reduced at measured test 

concentrations ranging from 3.75 to 18 mg TAN/L. TRAP analysis of biomass resulted in 

calculation of an EC20 of 1.85 mg TAN/L at pH 7.76 and 22.5°C (U.S. EPA 1999). The EC20

adjusted to pH 7 is 3.273 mg TAN/L (Appendix B).

The SMCV for the bluegill is 3.273 mg TAN/L, which, when calculated as a geometric 

mean with the SMCV of 14.63 mg TAN/L for green sunfish, results in a GMCV of 6.920 for the 

genus Lepomis (Table 4).

Musculium transversum

Anderson et al. (1978) conducted two 42-day tests of the effect of ammonia on survival 

of field-collected juvenile clams whose length averaged 2.2 mm. The results of the two tests 
38

were similar so the data were pooled for analysis. Survival in the control treatment and low 

ammonia concentrations (<5.1 mg TAN/L) ranged from 79 to 90%, but decreased to zero at 18 

mg TAN/L. TRAP analysis of the survival data resulted in a calculated EC20 of 5.820 mg 

TAN/L at 23.5°C and pH 8.15. The EC20 is 22.21 mg TAN/L when adjusted to pH 7 and 20°C 

(Appendix B).

Sparks and Sandusky (1981) conducted a test similar to Anderson et al. (1978) with fieldcollected juvenile clams whose average length was 2.1 mm. The test was conducted in the same 

laboratory and used test organisms from the same location in the Mississippi River as Anderson 

et al. (1978), but employed a feeding regime and food for the test that was deemed by the authors 

to be better suited to maintaining the health of fingernail clams during chronic toxicity testing. 

Survival in the control treatment was 92% and decreased with increasing concentration of 

ammonia to 17% at 18 mg TAN/L. Effects on survival were evident at lower concentrations, 

resulting in an EC20 of only 1.23 mg TAN/L at 21.8°C and pH 7.80 when calculated using 

TRAP. The EC20 adjusted to pH 7 and 20°C is 2.565 mg TAN/L (Appendix B). 

Although this latter EC20 determined for the test reported by Sparks and Sandusky (1981) 

is substantially lower than that obtained by Anderson et al. (1978), the difference is less than a 

factor of 10, and thus, the SMCV for this species (at pH 7 and 20°C) is the geometric mean of the 

two values, or 7.547 mg TAN/L (Table 4). 
39

Table 4. Ranked Genus Mean Chronic Values.

Rank

GMCV 

(mg TAN/L) Species

SMCV 

(mg TAN/L)

16 73.74 Stonefly,

Pteronarcella badia 73.74

15 53.75

Water flea,

Ceriodaphnia acanthina 64.10

Water flea,

Ceriodaphnia dubia 45.08

14 41.46 Water flea,

Daphnia magna 41.46

13 29.17 Amphipod,

Hyalella azteca 29.17

12 21.36 Channel catfish,

Ictalurus punctatus 21.36

11 20.38 Northern pike,

Esox lucius 20.38

10 16.53 Common carp,

Cyprinus carpio 16.53

9 12.02

Lahontan cutthroat trout,

Oncorhynchus clarkii henshawi

(LS)*

25.83

Rainbow trout,

Oncorhynchus mykiss (LS) 6.663

Sockeye salmon,

Oncorhynchus nerka (LS) 10.09

8 11.62 White sucker,

Catostomus commersonii 11.62

7 11.07 Smallmouth bass,

Micropterus dolomieu 11.07

6 9.187 Fathead minnow,

Pimephales promelas 9.187

5 7.828 Pebblesnail,

Fluminicola sp.

7.828

4 7.547 Long fingernailclam,

Musculium transversum 7.547

3 6.920

Green sunfish,

Lepomis cyanellus 14.63

Bluegill,

Lepomis macrochirus 3.273

2 3.501 Rainbow mussel,

Villosa iris 3.501

1 2.126

Fatmucket,

Lampsilis siliquoidea 3.211

Wavy-rayed lamp mussel,

Lampsilis fasciola 1.408

FCV = 1.887 mg TAN/L

CCC = 1.9 mg TAN/L

LS= Federally-listed species as threatened or endangered

LS* = Listed at the subspecies only for specific populations
40

The National Criteria for Ammonia in Fresh Water

This ammonia criteria update document recommends an acute criterion magnitude of 17

mg TAN/L and a chronic criterion magnitude of 1.9 mg TAN/L at pH 7 and 20°C, with the 

stipulation that the chronic criterion cannot exceed 4.8 mg TAN/L as a 4-day average. All 

criteria magnitudes are recommended not to be exceeded more than once in three years on 

average. 

2013 Final Aquatic Life Criteria for Ammonia

(Magnitude, Frequency, and Duration)

(mg TAN/L)

pH 7.0, T=20°C

Acute

(1-hour average) 17

Chronic

(30-day rolling average) 1.9*

*Not to exceed 2.5 times the CCC as a 4-day average within 

the 30-days, i.e. 4.8 mg TAN/L at pH 7 and 20°C, more than 

once in three years on average.

Criteria frequency: Not to be exceeded more than once in 

three years on average.

The available data for ammonia indicate that, except possibly where an unusually 

sensitive species is important at a site, freshwater aquatic life will be protected if these criteria 

are met. Tables 5a and 5b below provide the temperature and pH-dependent values of the CMC 

(acute criterion magnitude) and Table 6 provides the temperature and pH-dependent values of 

the CCC (chronic criterion magnitude) based on the following recommended criterion 

calculations derived for this update.

Acute criterion calculations

The one-hour average concentration of total ammonia nitrogen (in mg TAN/L) is not to

exceed, more than once every three years on the average, the CMC (acute criterion magnitude) 

calculated using the following equation: 
41

 ((

 

 

 

 ) 

( (

 

 

 

 ) ( ( )

)))

The 2013 CMC equation is predicated on the following:

1. The lowest GMAV in this criterion update is for an invertebrate species; thus, the CMC is 

both pH- and temperature-dependent and varies with temperature according to the invertebrate

acute temperature relationship. The lowest GMAV is 23.12 mg TAN/L for Venustaconcha 

(Table 3). The updated CMC (rounded to 4 significant figures) of 16.76 mg TAN/L at pH 7 and 

20°C is 27.5 percent lower than this value. The CMC divided by the lowest GMAV is 0.7249. 

2. Where salmonids in the Genus Oncorhynchus are present, EPA’s recommended acute

criterion magnitude is protective of the commercially and recreationally important adult rainbow 

trout, which becomes the most sensitive endpoint at lower temperatures (see footnotes pertaining 

to the 1999 FAV in Table 7 and Appendix A). Vertebrate sensitivity to ammonia is independent 

of temperature, while invertebrate sensitivity to ammonia decreases as temperature decreases. 

Therefore, across all temperatures the CMC equals the lower of: a) 0.7249 times the temperature 

adjusted lowest invertebrate GMAV (for Ellipse 23.12 mg TAN/L times 0.7249, or 16.76 mg 

TAN/L at pH 7.0 and 20oC), or (b) the FAV protective of adult rainbow trout (48.21 mg TAN/L) 

divided by two, or 24.10 mg TAN/L at pH 7.0 and across all temperatures, according to the 

following temperature relationship:

 ( ) ( ( ( ( ))))

Thus, the CMC increases with decreasing temperature as a result of increased invertebrate 

insensitivity until it reaches a plateau of 24.10 mg TAN/L at 15.7°C and below, where the most 

sensitive taxa is the temperature invariant rainbow trout (Table 5a; see also Oncorhynchus

present line in Figure 5a).
42

3. Where Oncorhynchus species are absent, EPA retains all tested species in the order 

Salmoniformes as tested surrogate species representing untested freshwater fish resident in the 

U.S. from another order, but does not lower the criterion to protect them as commercially and 

recreationally important species. The lowest GMAV for a freshwater fish is 51.93 mg TAN/L

for mountain whitefish (Prosopium williamsoni) (Table 3). Therefore, in this case, the CMC

equals the lower of: a) 0.7249 times the temperature adjusted lowest invertebrate GMAV (for 

Ellipse 23.12 mg TAN/L times 0.7249, or 16.76 mg TAN/L at pH 7.0 and 20oC), or (b) 0.7249

times the lowest freshwater fish GMAV (51.93 mg TAN/L at pH 7.0 and all temperatures), 

according to the following temperature relationship:

 ( ) ( ( ))

Thus, the CMC increases with decreasing temperature as a result of increased invertebrate 

insensitivity until it reaches a plateau of 37.65 mg TAN/L at 10.2°C and below (51.93 mg 

TAN/L x 0.7249), where the most sensitive taxa switches to the temperature invariant fish genus 

Prosopium (Table 5b; see also Oncorhynchus absent line in Figure 5a). Note: while the 

mountain whitefish (Prosopium williamsoni) is a species in the same family as Oncorhynchus

species (i.e., Family: Salmonidae), it is also an appropriately sensitive surrogate species amongst 

all freshwater fish in the Class Actinopterygii. 

The CMC, where Oncorhynchus species are absent, extrapolated across both temperature and pH 

is as follows:

 

 

 

 

 ( ( )

)

4. When a threatened or endangered species occurs at a site and sufficient data indicate that it is 

sensitive at 1-hour average concentrations below the CMC, it is appropriate to consider deriving 

a site-specific criterion magnitude. It should be noted that the dataset used to derive the 2013
43

ammonia criteria magnitudes included some threatened or endangered species, none of which 

were the most sensitive of the species tested.

In summary, at pH 7 and 20°C the CMC is 17 mg TAN/L, as primarily determined by the 

sensitivity of invertebrates. As temperature decreases to 15.7°C and below, invertebrates no 

longer are the most sensitive taxa, and thus in this range the CMC is 24 mg TAN/L. Where 

recreationally and/or commercially important Oncorhynchus species are not present, the CMC is 

determined according to statement three above. Below 15.7°C, if Oncorhynchus species are not 

present the criterion continues to increase with decreasing temperature to 10.2°C and below,

where the CMC is 38 mg TAN/L.

Figure 5a. 2013 Acute Criterion Magnitudes Extrapolated Across a Temperature Gradient 

at pH 7.

Temperature (°C)

0 5 10 15 20 25 30

CMC at pH 7 (mg TAN/L)

0

10

20

30

40

2013 CMC - Oncorhynchus present

2013 CMC - Oncorhynchus absent
44

Table 5a. Temperature and pH-Dependent Values of the CMC (Acute Criterion Magnitude) – Oncorhynchus spp. Present.

Temperature (°C)

pH 0-14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

6.5 33 33 32 29 27 25 23 21 19 18 16 15 14 13 12 11 9.9

6.6 31 31 30 28 26 24 22 20 18 17 16 14 13 12 11 10 9.5

6.7 30 30 29 27 24 22 21 19 18 16 15 14 13 12 11 9.8 9.0

6.8 28 28 27 25 23 21 20 18 17 15 14 13 12 11 10 9.2 8.5

6.9 26 26 25 23 21 20 18 17 15 14 13 12 11 10 9.4 8.6 7.9

7.0 24 24 23 21 20 18 17 15 14 13 12 11 10 9.4 8.6 8.0 7.3

7.1 22 22 21 20 18 17 15 14 13 12 11 10 9.3 8.5 7.9 7.2 6.7

7.2 20 20 19 18 16 15 14 13 12 11 9.8 9.1 8.3 7.7 7.1 6.5 6.0

7.3 18 18 17 16 14 13 12 11 10 9.5 8.7 8.0 7.4 6.8 6.3 5.8 5.3

7.4 15 15 15 14 13 12 11 9.8 9.0 8.3 7.7 7.0 6.5 6.0 5.5 5.1 4.7

7.5 13 13 13 12 11 10 9.2 8.5 7.8 7.2 6.6 6.1 5.6 5.2 4.8 4.4 4.0

7.6 11 11 11 10 9.3 8.6 7.9 7.3 6.7 6.2 5.7 5.2 4.8 4.4 4.1 3.8 3.5

7.7 9.6 9.6 9.3 8.6 7.9 7.3 6.7 6.2 5.7 5.2 4.8 4.4 4.1 3.8 3.5 3.2 3.0

7.8 8.1 8.1 7.9 7.2 6.7 6.1 5.6 5.2 4.8 4.4 4.0 3.7 3.4 3.2 2.9 2.7 2.5

7.9 6.8 6.8 6.6 6.0 5.6 5.1 4.7 4.3 4.0 3.7 3.4 3.1 2.9 2.6 2.4 2.2 2.1

8.0 5.6 5.6 5.4 5.0 4.6 4.2 3.9 3.6 3.3 3.0 2.8 2.6 2.4 2.2 2.0 1.9 1.7

8.1 4.6 4.6 4.5 4.1 3.8 3.5 3.2 3.0 2.7 2.5 2.3 2.1 2.0 1.8 1.7 1.5 1.4

8.2 3.8 3.8 3.7 3.5 3.1 2.9 2.7 2.4 2.3 2.1 1.9 1.8 1.6 1.5 1.4 1.3 1.2

8.3 3.1 3.1 3.1 2.8 2.6 2.4 2.2 2.0 1.9 1.7 1.6 1.4 1.3 1.2 1.1 1.0 0.96

8.4 2.6 2.6 2.5 2.3 2.1 2.0 1.8 1.7 1.5 1.4 1.3 1.2 1.1 1.0 0.93 0.86 0.79

8.5 2.1 2.1 2.1 1.9 1.8 1.6 1.5 1.4 1.3 1.2 1.1 0.98 0.90 0.83 0.77 0.71 0.65

8.6 1.8 1.8 1.7 1.6 1.5 1.3 1.2 1.1 1.0 0.96 0.88 0.81 0.75 0.69 0.63 0.59 0.54

8.7 1.5 1.5 1.4 1.3 1.2 1.1 1.0 0.94 0.87 0.80 0.74 0.68 0.62 0.57 0.53 0.49 0.45

8.8 1.2 1.2 1.2 1.1 1.0 0.93 0.86 0.79 0.73 0.67 0.62 0.57 0.52 0.48 0.44 0.41 0.37

8.9 1.0 1.0 1.0 0.93 0.85 0.79 0.72 0.67 0.61 0.56 0.52 0.48 0.44 0.40 0.37 0.34 0.32

9.0 0.88 0.88 0.86 0.79 0.73 0.67 0.62 0.57 0.52 0.48 0.44 0.41 0.37 0.34 0.32 0.29 0.27
45

Table 5b. Temperature and pH-Dependent Values of the CMC (Acute Criterion Magnitude) – Oncorhynchus spp. Absent.

Temperature (°C)

pH 0-10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

6.5 51 48 44 41 37 34 32 29 27 25 23 21 19 18 16 15 14 13 12 11 9.9

6.6 49 46 42 39 36 33 30 28 26 24 22 20 18 17 16 14 13 12 11 10 9.5

6.7 46 44 40 37 34 31 29 27 24 22 21 19 18 16 15 14 13 12 11 9.8 9.0

6.8 44 41 38 35 32 30 27 25 23 21 20 18 17 15 14 13 12 11 10 9.2 8.5

6.9 41 38 35 32 30 28 25 23 21 20 18 17 15 14 13 12 11 10 9.4 8.6 7.9

7.0 38 35 33 30 28 25 23 21 20 18 17 15 14 13 12 11 10 9.4 8.6 7.9 7.3

7.1 34 32 30 27 25 23 21 20 18 17 15 14 13 12 11 10 9.3 8.5 7.9 7.2 6.7

7.2 31 29 27 25 23 21 19 18 16 15 14 13 12 11 9.8 9.1 8.3 7.7 7.1 6.5 6.0

7.3 27 26 24 22 20 18 17 16 14 13 12 11 10 9.5 8.7 8.0 7.4 6.8 6.3 5.8 5.3

7.4 24 22 21 19 18 16 15 14 13 12 11 9.8 9.0 8.3 7.7 7.0 6.5 6.0 5.5 5.1 4.7

7.5 21 19 18 17 15 14 13 12 11 10 9.2 8.5 7.8 7.2 6.6 6.1 5.6 5.2 4.8 4.4 4.0

7.6 18 17 15 14 13 12 11 10 9.3 8.6 7.9 7.3 6.7 6.2 5.7 5.2 4.8 4.4 4.1 3.8 3.5

7.7 15 14 13 12 11 10 9.3 8.6 7.9 7.3 6.7 6.2 5.7 5.2 4.8 4.4 4.1 3.8 3.5 3.2 2.9

7.8 13 12 11 10 9.3 8.5 7.9 7.2 6.7 6.1 5.6 5.2 4.8 4.4 4.0 3.7 3.4 3.2 2.9 2.7 2.5

7.9 11 9.9 9.1 8.4 7.7 7.1 6.6 3.0 5.6 5.1 4.7 4.3 4.0 3.7 3.4 3.1 2.9 2.6 2.4 2.2 2.1

8.0 8.8 8.2 7.6 7.0 6.4 5.9 5.4 5.0 4.6 4.2 3.9 3.6 3.3 3.0 2.8 2.6 2.4 2.2 2.0 1.9 1.7

8.1 7.2 6.8 6.3 5.8 5.3 4.9 4.5 4.1 3.8 3.5 3.2 3.0 2.7 2.5 2.3 2.1 2.0 1.8 1.7 1.5 1.4

8.2 6.0 5.6 5.2 4.8 4.4 4.0 3.7 3.4 3.1 2.9 2.7 2.4 2.3 2.1 1.9 1.8 1.6 1.5 1.4 1.3 1.2

8.3 4.9 4.6 4.3 3.9 3.6 3.3 3.1 2.8 2.6 2.4 2.2 2.0 1.9 1.7 1.6 1.4 1.3 1.2 1.1 1.0 0.96

8.4 4.1 3.8 3.5 3.2 3.0 2.7 2.5 2.3 2.1 2.0 1.8 1.7 1.5 1.4 1.3 1.2 1.1 1.0 0.93 0.86 0.79

8.5 3.3 3.1 2.9 2.7 2.4 2.3 2.1 1.9 1.8 1.6 1.5 1.4 1.3 1.2 1.1 0.98 0.90 0.83 0.77 0.71 0.65

8.6 2.8 2.6 2.4 2.2 2.0 1.9 1.7 1.6 1.5 1.3 1.2 1.1 1.0 0.96 0.88 0.81 0.75 0.69 0.63 0.58 0.54

8.7 2.3 2.2 2.0 1.8 1.7 1.6 1.4 1.3 1.2 1.1 1.0 0.94 0.87 0.80 0.74 0.68 0.62 0.57 0.53 0.49 0.45

8.8 1.9 1.8 1.7 1.5 1.4 1.3 1.2 1.1 1.0 0.93 0.86 0.79 0.73 0.67 0.62 0.57 0.52 0.48 0.44 0.41 0.37

8.9 1.6 1.5 1.4 1.3 1.2 1.1 1.0 0.93 0.85 0.79 0.72 0.67 0.61 0.56 0.52 0.48 0.44 0.40 0.37 0.34 0.32

9.0 1.4 1.3 1.2 1.1 1.0 0.93 0.86 0.79 0.73 0.67 0.62 0.57 0.52 0.48 0.44 0.41 0.37 0.34 0.32 0.29 0.27
46

Chronic criterion calculations

The thirty-day rolling average concentration of total ammonia nitrogen (in mg TAN/L) is

not to exceed, more than once every three years on the average, the chronic criterion magnitude

(CCC) calculated using the following equation:

 (

 

 

 

 ) ( ( ( ))

)

In addition, the highest four-day average within the 30-day averaging period should not 

be more than 2.5 times the CCC (e.g., 2.5 x 1.9 mg TAN/L at pH 7 and 20°C or 4.8 mg TAN/L)

more than once in three years on average.

The 2013 CCC equation is predicated on the following:

1. The lowest GMCV in this criteria update is for an invertebrate species; thus, the CCC is both 

pH- and temperature-dependent (based on the invertebrate chronic temperature relationship). 

The lowest GMCV is 2.126 mg TAN/L for Villosa iris (Table 4). The updated CCC (rounded to

4 significant figures) of 1.887 mg TAN/L at pH 7and 20°C is 11.2 percent lower than the lowest 

GMCV. The CCC to lowest GMCV ratio is 0.8876. 

2. The most sensitive freshwater fish to chronic ammonia exposure are early life stages of 

Lepomis with a GMCV of 6.920 mg TAN/L (Table 4). At a pH of 7 and temperature of 7°C and

below, the CCC plateaus (see Figure 5b) at 4.363 mg TAN/L, which is lower than the GMCV for

Lepomis, the most sensitive fish, multiplied by the CCC to lowest GMCV ratio (or 6.920 mg 

TAN/L x 0.8876 = 6.142 mg TAN/L); thus, at pH 7, the CCC is expressed as:

 ( ( ( )))

This function increases steadily with decreasing temperature (T), until it reaches a maximum at 

7°C, below which it remains constant (see Table 6; also shown graphically in Figure 5b). The 

rationale for the 7°C plateau in extrapolated invertebrate sensitivities is described in detail in 
47

Appendix M. The assumption of invertebrate insensitivity to temperatures of 7°C and below is 

based on an interpretation of the empirical relationship between acute ammonia toxicity of 

invertebrates and temperature, first described by Arthur et al. (1987), and in Appendix M).

3. All new chronic fish data added to this update of the freshwater AWQC for ammonia are 

from early life-stage tests of the species (see new data for Oncorhynchus clarkii henshawi, 

Oncorhynchus mykiss, Esox lucius, and Cyprinus carpio in Appendix B), and since the new 

chronic criterion magnitude lies far below all chronic values for these fishes (as well as for 

Lepomis spp.), the early life stage of fish no longer warrants special consideration.

4. Where a threatened or endangered species occurs at a site and sufficient data indicate that it is 

sensitive at concentrations below the CCC, it is appropriate to consider deriving a site-specific 

criterion magnitude.

In summary, at pH 7 and 20°C the CCC of 1.9 mg TAN/L is determined by the 

sensitivity of invertebrates. As temperature decreases, invertebrate sensitivity to ammonia 

decreases until the CCC reaches a maximum of 4.4 mg TAN/L at pH 7 and temperature of 7°C 

and below.
48

Figure 5b. 2013 Chronic Criterion Magnitudes Extrapolated Across a Temperature 

Gradient at pH 7.
49

Table 6. Temperature and pH-Dependent Values of the CCC (Chronic Criterion Magnitude).

Temperature (°C)

pH 0-7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

6.5 4.9 4.6 4.3 4.1 3.8 3.6 3.3 3.1 2.9 2.8 2.6 2.4 2.3 2.1 2.0 1.9 1.8 1.6 1.5 1.5 1.4 1.3 1.2 1.1

6.6 4.8 4.5 4.3 4.0 3.8 3.5 3.3 3.1 2.9 2.7 2.5 2.4 2.2 2.1 2.0 1.8 1.7 1.6 1.5 1.4 1.3 1.3 1.2 1.1

6.7 4.8 4.5 4.2 3.9 3.7 3.5 3.2 3.0 2.8 2.7 2.5 2.3 2.2 2.1 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.2 1.1

6.8 4.6 4.4 4.1 3.8 3.6 3.4 3.2 3.0 2.8 2.6 2.4 2.3 2.1 2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.1

6.9 4.5 4.2 4.0 3.7 3.5 3.3 3.1 2.9 2.7 2.5 2.4 2.2 2.1 2.0 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.2 1.1 1.0

7.0 4.4 4.1 3.8 3.6 3.4 3.2 3.0 2.8 2.6 2.4 2.3 2.2 2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.1 0.99

7.1 4.2 3.9 3.7 3.5 3.2 3.0 2.8 2.7 2.5 2.3 2.2 2.1 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.2 1.1 1.0 0.95

7.2 4.0 3.7 3.5 3.3 3.1 2.9 2.7 2.5 2.4 2.2 2.1 2.0 1.8 1.7 1.6 1.5 1.4 1.3 1.3 1.2 1.1 1.0 0.96 0.90

7.3 3.8 3.5 3.3 3.1 2.9 2.7 2.6 2.4 2.2 2.1 2.0 1.8 1.7 1.6 1.5 1.4 1.3 1.3 1.2 1.1 1.0 0.97 0.91 0.85

7.4 3.5 3.3 3.1 2.9 2.7 2.5 2.4 2.2 2.1 2.0 1.8 1.7 1.6 1.5 1.4 1.3 1.3 1.2 1.1 1.0 0.96 0.90 0.85 0.79

7.5 3.2 3.0 2.8 2.7 2.5 2.3 2.2 2.1 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.2 1.1 1.0 0.95 0.89 0.83 0.78 0.73

7.6 2.9 2.8 2.6 2.4 2.3 2.1 2.0 1.9 1.8 1.6 1.5 1.4 1.4 1.3 1.2 1.1 1.1 0.98 0.92 0.86 0.81 0.76 0.71 0.67

7.7 2.6 2.4 2.3 2.2 2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.1 1.0 0.94 0.88 0.83 0.78 0.73 0.68 0.64 0.60

7.8 2.3 2.2 2.1 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.2 1.1 1.0 0.95 0.89 0.84 0.79 0.74 0.69 0.65 0.61 0.57 0.53

7.9 2.1 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.2 1.1 1.0 0.95 0.89 0.84 0.79 0.74 0.69 0.65 0.61 0.57 0.53 0.50 0.47

8.0 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.1 1.0 0.94 0.88 0.83 0.78 0.73 0.68 0.64 0.60 0.56 0.53 0.50 0.44 0.44 0.41

8.1 1.5 1.5 1.4 1.3 1.2 1.1 1.1 0.99 0.92 0.87 0.81 0.76 0.71 0.67 0.63 0.59 0.55 0.52 0.49 0.46 0.43 0.40 0.38 0.35

8.2 1.3 1.2 1.2 1.1 1.0 0.96 0.90 0.84 0.79 0.74 0.70 0.65 0.61 0.57 0.54 0.50 0.47 0.44 0.42 0.39 0.37 0.34 0.32 0.30

8.3 1.1 1.1 0.99 0.93 0.87 0.82 0.76 0.72 0.67 0.63 0.59 0.55 0.52 0.49 0.46 0.43 0.40 0.38 0.35 0.33 0.31 0.29 0.27 0.26

8.4 0.95 0.89 0.84 0.79 0.74 0.69 0.65 0.61 0.57 0.53 0.50 0.47 0.44 0.41 0.39 0.36 0.34 0.32 0.30 0.28 0.26 0.25 0.23 0.22

8.5 0.80 0.75 0.71 0.67 0.62 0.58 0.55 0.51 0.48 0.45 0.42 0.40 0.37 0.35 0.33 0.31 0.29 0.27 0.25 0.24 0.22 0.21 0.20 0.18

8.6 0.68 0.64 0.60 0.56 0.53 0.49 0.46 0.43 0.41 0.38 0.36 0.33 0.31 0.29 0.28 0.26 0.24 0.23 0.21 0.20 0.19 0.18 0.16 0.15

8.7 0.57 0.54 0.51 0.47 0.44 0.42 0.39 0.37 0.34 0.32 0.30 0.28 0.27 0.25 0.23 0.22 0.21 0.19 0.18 0.17 0.16 0.15 0.14 0.13

8.8 0.49 0.46 0.43 0.40 0.38 0.35 0.33 0.31 0.29 0.27 0.26 0.24 0.23 0.21 0.20 0.19 0.17 0.16 0.15 0.14 0.13 0.13 0.12 0.11

8.9 0.42 0.39 0.37 0.34 0.32 0.30 0.28 0.27 0.25 0.23 0.22 0.21 0.19 0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.12 0.11 0.10 0.09

9.0 0.36 0.34 0.32 0.30 0.28 0.26 0.24 0.23 0.21 0.20 0.19 0.18 0.17 0.16 0.15 0.14 0.13 0.12 0.11 0.11 0.10 0.09 0.09 0.08
50

Additional explanation and justification supporting the 2013 temperature and pHdependent calculations and criteria magnitudes

Part of a criterion magnitude derivation is the estimation of the CMC or CCC based on 

the set of toxicity values available for different genera. The CMC or CCC estimate is intended to 

be equivalent to what would be obtained by simple inspection if many genera had been tested. 

Generally, the CMC or CCC is below the lowest value. For small datasets (<19) it is assumed 

that the fifth percentile is lower than the lowest toxicity value. Because the CMC is one half of 

the fifth percentile (i.e., FAV/2), it is frequently lower than the lowest GMAV even in large 

datasets. Because the extrapolation procedure used to calculate the FAV or FCV/CCC is based 

on the slope of the four most sensitive genera, when there are data for less than 59 genera, if the 

genera vary widely in sensitivity, the extrapolated criterion value is further below the lowest 

value than if the criteria were tightly grouped. This is statistically appropriate because when 

variance is high (i.e., values are widely spaced), the fifth percentile of the distribution would be 

expected to lie further below the lowest value of a small dataset than if the variance was low.

This extrapolation procedure, while appropriate for criteria derivations across chemicals 

with different variances for genus sensitivities, is not necessarily appropriate when the genera are 

following different temperature or life stage dependencies. Sensitivities can change with 

temperature or life stage, and as a result, the spread of the four lowest GMAVs or GMCVs, and 

the resulting degree of extrapolation to the fifth percentile of sensitivity, can also change. Rather 

than develop separate sets of GMAVs and GMCVs for each temperature and re-computing 

iteratively the CMC or CCC from the four most sensitive GMAVs or GMCVs at each 

temperature-pH combination, the extrapolation approach described below was used.

This issue of extrapolation to different temperatures and pH values with regard to chronic 

toxicity was addressed in the 1999 AWQC document for ammonia by first calculating the ratio 

of the CCC to the lowest GMCV, and then applying that ratio to subsequent criteria calculations 

for all possible pH and temperature combinations. The rationale of this approach was that it 

offered a degree of extrapolation that was modest and reasonable given the relatively low 

number of tested genera, and that it was a preferable approach to the alternative procedure of 

calculating CCCs directly from new sets of GMCVs for each pH-temperature combination, as 

each combination could result in different degrees of extrapolation, some of which could be 

more than 50 percent below the lowest GMCV.
51

In the 1999 AWQC document, the temperature extrapolations for the CCC determination 

described above were conducted separately for adult fish, fish early life stages, and invertebrates. 

This was because fish GMCVs are not affected by temperature, and because the most sensitive 

fish species was an early life stage of Lepomis. As a consequence, even though the lowest 

GMCV at 20°C was for an invertebrate, as temperature decreases, invertebrates, but not fish, 

become less sensitive to ammonia, and below 14.6°C, fish genera become the most sensitive. 

However, the above scenario is not applicable now because at the new recommended CCC (1.9 

mg TAN/L), invertebrate genera are the most sensitive across the entire temperature range.

In the 1999 AWQC document, the most sensitive GMAVs were for fish, and because the 

sensitivities of fish to ammonia did not vary with temperature, no temperature extrapolation was 

performed. In contrast, the lowest GMAVs in this document are for invertebrates, and as a 

consequence, the temperature extrapolation procedure is similarly applied to the CMC as well as 

the CCC.

For the reassessment of the pH-TAN acute toxicity relationship, EPA has determined that 

the current pH-TAN acute toxicity relationship equation effectively represents the pH-TAN 

toxicity relationship for L. siliquoidea (as determined by Wang et al. 2008), as well as for other 

invertebrates, Potamopyrgus antipodarum (snail), Macrobrachium rosenbergii (freshwater 

shrimp), and H. azteca (amphipod), as tested by Hickey and Vickers (1994), Straus et al. (1991), 

and Borgmann and Borgmann (1997), respectively. Also, for the reassessment of the 

temperature-TAN acute toxicity relationship, EPA similarly determined that the current 

temperature-TAN acute toxicity relationship equation effectively represents the temperatureTAN toxicity relationship for other invertebrates, P. antipodarum (snail), Branchiura sowerbyi

(oligochaete), and Viviparus bengalensis (snail) as tested by Hickey and Vickers (1994) and 

Sarkar (1997), respectively.

Protection of downstream waters

EPA regulations at 40 CFR 131.10(b) provide that “[i]n designating uses of a water body 

and the appropriate criteria for those uses, the state shall take into consideration the water quality 

standards of downstream waters and ensure that its water quality standards provide for the 

attainment and maintenance of the water quality standards of downstream waters.” In cases 

where downstream waters are characterized by higher pH and/or temperature, or harbor more 
52

sensitive species, ammonia criteria more stringent than those required to protect in-stream uses 

may be necessary in order to ensure that water quality standards provide for the attainment and 

maintenance of the water quality standards of downstream waters.

Considerations for site-specific criteria derivation

At water temperatures above 15.7°C, the 2013 acute criteria magnitude is based on 

effects to freshwater unionid mussels. However, when the temperature is below 15.7°C, and 

salmonids are present (even when mussels or other sensitive mollusk species are present), 

salmonid sensitivity determines the acute criterion (regardless of pH), similar to the 1999 acute 

criterion, which was based on effects on salmonids (i.e., adult rainbow trout). Where unionid 

mussels and other sensitive related mollusk species are absent, the commercially and 

recreationally important adult rainbow trout is the most sensitive species. Site-specific criteria 

derivation must take into account the temperature at the site. As an example, the acute criterion 

magnitude at pH 7 and temperature 20°C cannot exceed 24 mg TAN/L (the rainbow trout SMAV 

of 48.21 mg TAN/L, divided by two, used in this 2013 update as being representative of the most 

sensitive fish in general).

The 1999 chronic criterion (CCC) magnitude was based on the effects on fish early life 

stages, whereas based on the new data, the 2013 CCC magnitude is based on the effects on 

sensitive invertebrate genera, including unionid mussels. When mussels are present, the 2013 

CCC magnitude is protective of fish early life stages regardless of temperature. See Appendix N 

for additional information on site-specific criteria for ammonia.

EFFECTS CHARACTERIZATION

The purpose of this section is to characterize the potential effects of ammonia on aquatic 

life considering available test data and to describe additional lines of evidence not used directly 

in the criteria calculations, but which support the 2013 aquatic life criteria values. This section 

will also provide a summary of the uncertainties and assumptions, as well as provide 

explanations for decisions regarding data acceptability and usage in the effects assessment. In 

addition, this section will describe substantive differences between the 1999 ammonia AWQC 

and the 2013 update resulting from the incorporation of the latest scientific knowledge.
53

All acceptable acute and chronic values for freshwater aquatic animal species, including 

those from the 1999 AWQC document (re-normalized to pH 7 and 20°C in the case of 

invertebrates), are presented in Appendices A (acute) and B (chronic). These tables include new 

acute and chronic ammonia toxicity data for freshwater mussels in the Family Unionidae and 

reflect the latest science informing the determinations regarding acceptable test conditions and 

associated data for glochidia and juvenile mussels. 

Freshwater Acute Toxicity Data

Acute toxicity data for freshwater mussels and non-pulmonate (gill-bearing) snails

Prior to publishing the 2009 draft ammonia AWQC, concerns had been raised about the 

appropriateness of using data obtained from tests conducted with the parasitic glochidia lifestage of freshwater unionid mussels. Glochidia of different species have different life history 

strategies for finding an appropriate fish host; glochidia may be free living in the water column 

(and potentially exposed to pollutants) for a duration ranging from seconds to days, depending 

on the particular species. EPA concluded it was useful to consider potential adverse effects on 

glochidia, because effects of chemicals on this early life stage of mussels could potentially have

broad impacts on mussel populations. In order for the toxicity test results with glochidia to be 

ecologically relevant, the duration of the acute toxicity test must be comparable to the duration of 

the free-living stage of the glochidia prior to attaching to a host. Supported by research 

conducted by Bringolf et al. (2013) demonstrating the appropriate duration of exposure for this 

life stage, acceptable acute toxicity data for glochidia with an exposure duration of 24 hours or 

less have been included in this 2013 AWQC Update, with the stipulation that control survival for 

the time period used is at least 90%.

In addition to the four sensitive bivalve mollusk species in Table 7, there are three other 

unionid mussel species among the seven genera found to be most acutely sensitive to ammonia

as well as two non-pulmonate snail species are ranked tenth and twelfth in sensitivity. These 

GMAVs represent mollusk toxicity data that were not in the 1999 acute criteria dataset.

New test data for the ellipse (Venustaconcha ellipsiformis), the most sensitive species 

tested, was not directly used in the acute criterion calculation because the methodology used 

calculated the acute value using the second through fifth most sensitive species to approximate 

effects for a 5th percentile of species as noted in the effects assessment. The GMAV for ellipse 
54

(23.12 mg TAN/L at pH 7 and 20°C) is greater than the acute criterion of 17 mg TAN/L and thus 

provides additional evidence supporting the protectiveness of the calculated acute criterion 

(Table 3). 

Available data on non-pulmonate snails show that they are another taxon within the 

Phylum Mollusca sensitive to ammonia in freshwater ecosystems. The calculated GMAV of 

62.15 mg TAN/L for Fluminicola sp. (pebblesnail) is the tenth most sensitive in the acute dataset 

(Table 3). Another non-pulmonate snail species Pleurocera uncialis (pagoda hornsnail) was 

ranked 12th in acute sensitivity. The LC50 for P. uncialis (reported in Goudreau et al. 1993),

normalized to pH 7 and 20°C, is 68.54 mg TAN/L (Appendix A). To date, few studies have 

been attempted with this group of species; additional testing would improve understanding of 

their relative sensitivity to ammonia compared to other aquatic animals.

The draft 2009 acute criterion magnitude recommended for waters with mussels present 

was slightly higher than the 2013 acute criteria (19 vs. 17 mg TAN/L at pH 7, T 20°C) due to a 

number of differences in the data used in the CMC derivations. In response to comments

received on the 2009 draft criteria, EPA removed the six invasive species from the acute dataset 

for ammonia; one of the invasive species removed from the dataset was Asiatic clam, which had 

been ranked as the fourth most sensitive GMAVs in the 2009 draft AWQC. Because the acute 

dataset for ammonia is extensive and contains toxicity data for other bivalves that are native 

North American species, the Asiatic clam was not needed as a bivalve surrogate. Also in the 

2013 CMC, the most sensitive GMAV used to derive the CMC is for Lasmigona subviridis

(green floater mussel) (GMAV=23.41 mg TAN/L) which is lower than the lowest GMAV (32.73 

mg TAN/L) in the draft 2009 CMC used in the derivation of the CMC. Based on new scientific 

information regarding determination of test acceptability, EPA included acceptable data for 

glochidia (mussel larvae) and Hyalella azteca, which added five GMAVs for derivation of the 

CMC. Since the number of GMAVs is a factor in the equation used to derive the CMC, a change 

to the number of GMAVs results in a change in the resulting FAV and CMC.
55

Table 7. Comparison of the Four Taxa Used to Calculate the FAV and CMC in the 1999, 2009 Draft and 2013 AWQC.

1999 Update CMC Magnitude 2009 Draft Update CMC Magnitude 2013 Final CMC Magnitude

Species

pH 8.0,

T=25°C

(mg TAN/L)

pH 7.0,

T=20°C

(mg TAN /L) Species

pH 8.0,

T=25°C

(mg TAN/L)

pH 7.0,

T=20°C

(mg TAN/L) Species

pH 7.0,

T=20°C

(mg TAN/L)

Oncorhynchus sp. 

(salmonids), includes: 

O. aquabonita, O. clarkii, 

O. gorbuscha, O. kisutch, 

O. mykiss, and 

O. tshawytscha

21.95 99.15 Oyster mussel,

Epioblasma capsaeformis 6.037 39.24

Lampsilis sp.

(Unionidae), includes:

L. abrupta, L. cardium, 

L. fasciola, L. higginsii, L. 

rafinesqueana, and 

L. siliquoidea

46.63

Orangethroat darter, 

Etheostoma spectabile 17.96 74.25 Asiatic clam,Corbicula fluminea 6.018 39.12 Rainbow mussel,Villosa iris 34.23

Golden shiner, 

Notemigonus crysoleucas 14.67 63.02

Lampsilis sp.

(Unionidae), includes:

L. abrupta, L. cardium, 

L. fasciola, L. higginsii, 

L. rafinesqueana, and 

L. siliquoidea

5.919 38.48

Oyster mussel, 

Epioblasma capsaeformis 31.14

Mountain whitefish, 

Prosopium williamsoni 12.11 51.93 Rainbow mussel,Villosa iris 5.036 32.73 Green floater,Lasmigona subviridis 23.41

FAV1

11.23 48.21 FAV 5.734 37.27 FAV 33.52

CMC 5.6 24 CMC 2.9 19 CMC 17

 

1 The FAV in the 1999 AWQC document of 11.23 mg TAN/L at pH 8 was lowered to the geometric mean of these seven LC50 values at the time in order to 

protect large rainbow trout which were shown in Thurston and Russo (1983) to be measurably more sensitive than other life stages. The FAV prior to adjusting 

it to protect the commercially and recreationally important adult rainbow trout was calculated to be 14.32 mg TAN/L (CMC = 7.2 mg TAN/L) at pH 8. This 

FAV based on protection of adult rainbow trout at pH 7 is 48.21 mg TAN/L (see also Appendix A in this document).
56

Freshwater Chronic Toxicity Data

Use of 28-day juvenile unionid mussel data

EPA decided that growth data from 28-day tests with juvenile unionid mussels presented 

in the Wang et al. studies from 2007 and 2011 would not be used in calculating the 2013 chronic 

criterion. The decision not to use the growth data was based on the uncertainty in the test 

methods for assessing the growth endpoint and the need, as stated by the authors, for additional 

research “to optimize feeding conditions, to conduct longer-term exposures (e.g., 90 d), and to 

compare growth effect to potential reproductive effect in partial life-cycle exposure” (Wang et al. 

2011). The growth endpoint showed a high degree of variability, and the test methods for 

assessing growth, based on substrate or water-only exposures, are currently being evaluated. For 

these reasons, the survival data for 28-day juvenile mussels were used in the calculation of the 

CCC and not the growth data. Appendix G provides the TRAP EC20s for survival for rainbow 

mussel and both Lampsilis species, and a comparison to the growth of fatmucket mussel from 

28-day tests reported by Wang et al. (2007a, 2011), which shows the additional uncertainty in the 

concentration-response relationship based on growth.

28-day toxicity data for freshwater snails

As noted in the 2009 draft ammonia criteria document, non-pulmonate snails have been 

demonstrated to be sensitive to ammonia in freshwater ecosystems, in addition to other taxa 

within the Phylum Mollusca. Besser et al. (2010) data from a repeat test with pebblesnail 

(referred to in this document as Besser 2011) support the conclusion that non-pulmonate snails

may be slightly less sensitive to ammonia than freshwater mussels. Additional toxicity tests are 

recommended for non-pulmonate snails and other freshwater mollusks to further substantiate the 

findings from the 28-day tests summarized in Appendices H and I. The calculated EC20 values 

using TRAP for P. idahoensis, F. aldrichi, and T. serptenticola, and the recommended 28-day 

ammonia survival effects concentration of <7.667 mg TAN/L for P. canaliculata, are considered

representative of non-pulmonate snail sensitivity in general and are included in Appendix C for 

the purpose of comparison.

Based on the 28-day toxicity test results for the gill-bearing, non-pulmonate snail species 

(Appendices B and C), EPA concludes that the overall sensitivity of this particular group of snail 

species (Sub-class Prosobranchia, Order Neotaenioglossa) appears high. Furthermore, the 
57

sensitivity of juvenile and adult mixed-age non-pulmonate snails to ammonia may be greater 

than that of their air-breathing, pulmonate counterparts such as L. stagnalis.

Although the GMCV for Fluminicola species is not ranked as one of the four most 

sensitive used to calculate the FCV, the value is ranked the 5th most sensitive in the chronic 

criterion dataset. The 28-day growth EC20 for this freshwater non-pulmonate snail species,

calculated using EPA’s TRAP, is 2.281 mg TAN/L at test pH (8.22) and temperature (20.1°C), 

or 7.828 mg TAN/L after adjustment to pH 7 and 20°C (see Appendix B). Appendix H includes 

a summary of the 28-day toxicity test results for Fluminicola species which are acceptable for 

use quantitatively in the chronic dataset. The TRAP output for this test is provided in Appendix 

H.

28-day toxicity data for Hyalella azteca: Minimum Data Requirement Number 5

Literature data indicate that the response of Hyalella azteca is influenced not only by pH, 

but also by sodium concentration in the dilution water. Borgmann and Borgmann (1997) 

demonstrated that increasing sodium decreased the toxicity of ammonia to Hyalella, and applied 

these findings to explain differences in toxicity observed by Ankley et al. (1995), which were 

originally attributed to water hardness. Further unpublished experiments by EPA’s Office of 

Research and Development confirm Borgmann’s assertion that sodium concentration plays a key 

role in determining the acute response of Hyalella to ammonia (personal communication, D.R. 

Mount, EPA, ORD). Because sodium is not known to affect ammonia toxicity to other species, 

this criterion does not consider sodium concentration, and this variation is not explicitly 

addressed. For purposes of deriving a GMAV for Hyalella, tests were selected that had a 

moderate sodium concentration (e.g., “moderately hard” water tests from Ankley et al. 1995, see 

Appendix A), and tests with extremely low sodium concentrations were excluded (e.g., “soft” 

water tests from Ankley et al. 1995; data from Whiteman et al. 1996, see Appendix J). The 

available acute data for ammonia did not include tests conducted in natural waters with a sodium 

concentration below about 3 mg/L; at that sodium concentration, the acute values for Hyalella

were near the FAV reported in this document. Whether acute toxicity of ammonia to Hyalella

would occur below the FAV in waters with less than 3 mg/L sodium is unknown (Appendix H). 

For the 2013 chronic criterion, EPA re-evaluated the available data for Hyalella azteca

based on recent research regarding the appropriate test conditions, including water chemistry 
58

(e.g., appropriate concentrations for specific ions such as chloride) and feeding regimes. The 

concentrations of sodium are important to H. azteca health as discussed previously and the 

sodium concentrations in the chronic test used in the CCC represent approximately the midrange of U.S. waters. Based on this re-evaluation, EPA determined that certain tests met the new 

recommended conditions that would support healthy test organisms, and accepted those data for 

use in the calculation of the CCC. The specific tests used were from Borgmann (1994); details 

on these tests are included in Appendix H under Chronic Toxicity Tests with Juvenile Hyalella 

azteca. As a result of inclusion of acceptable H. azteca data, the minimum data requirement 

(MDR) for a benthic crustacean is fulfilled for the chronic criterion provided in this document. 

The GMCV of 29.17 mg TAN/L ranks Hyalella azteca as the thirteenth (of 16) most sensitive 

GMCV.
59

Reconsideration of the chronic toxicity data available for aquatic insects: Minimum Data 

Requirement Number 6

EPA chose not to include a chronic value for the stonefly, Pteronarcella badia, from 

Thurston et al. (1984a) in the 1999 AWQC update document because this aquatic insect species 

is relatively insensitive. Upon further consideration, EC20s for 30-day nymph mortality were 

calculated for field collected Pteronarcella badia for two separate partial life cycle tests in 

consecutive years, in order to develop a GMCV for insects to fulfill the sixth minimum data 

requirement (MDR), and to clearly specify the expected lack of sensitivity of insects to ammonia 

based on available data. EC20s were calculated for each test, and, as the authors themselves

noted, the results were variable between the two tests. The normalized EC20 for the test 

conducted with P. badia collected from the Gallatin R. was 207.0 mg TAN/L, and was 26.27 mg 

TAN/L for the test conducted with P. badia collected from the Rocky River (Appendix B). The 

geometric mean for these two tests is 73.74 mg TAN/L. It is not known if these tests were 

conducted using the most sensitive life stage; however, the authors did note that the length of 

individuals used in both tests was similar. EPA used the two EC20s based on 30-day nymph 

mortality to calculate a GMCV of 73.74 mg TAN/L for this species. The stonefly is listed as 

sixteenth GMCV in chronic sensitivity, fulfilling the sixth MDR. Additional data on insect 

sensitivity to ammonia would be useful in confirming the conclusion that insects are relatively

insensitive to ammonia in freshwater environments, given the limited data available. 

New chronic toxicity data for salmonid species and derivation of a GMCV for

Oncorhynchus: Minimum Data Requirement Number 1

Chronic values from two additional studies with Oncorhynchus species (salmonids) are 

included in this AWQC document that were not included in the 1999 document (see Appendix H 

for more detailed descriptions of the results from these studies). Koch et al. (1980) exposed 

Lahontan cutthroat trout (Oncorhynchus clarkii henshawi), an endangered species, for 103 days 

in an ELS test. There were no successful hatches at exposure levels of 148 mg TAN/L or higher

and no significant mortality at exposure levels below 32.9 mg TAN/L. Regression analysis of 

the survival data resulted in a calculated EC20 value of 17.89 mg TAN/L at 13.7°C and pH 7.57.

The EC20 value is 25.83 mg TAN/L when adjusted to pH 7 (Appendix B).
60

The results of a more recent 90-day ELS test using a wild strain of rainbow trout exposed 

to ammonia were reported by Brinkman et al. (2009), and are included in this criteria document. 

The test was initiated with newly fertilized embryos exposed under flow-through conditions 

through hatch, swim-up, and early fry development. Survival, growth and biomass of swim-up 

fry were significantly reduced at 16.8 mg TAN/L compared to controls, but unaffected at 7.44 

mg TAN/L. The EC20 calculated for biomass using TRAP and normalized to pH 7 is 15.60 mg 

TAN/L (Appendix B).

In the 1999 AWQC document, the results of six chronic tests conducted with ammonia 

for Oncorhynchus mykiss and Oncorhynchus nerka were included in Table 5 of that document as 

“acceptable” chronic tests for criteria development. A GMCV was not derived for 

Oncorhynchus at that time, however, because of the degree of variability among test results, as 

well as a preponderance of “greater than” or “less than” values, preventing the calculation of 

definitive SMCVs within the genus. The results of these chronic tests were only used at that 

time to assess the appropriateness of the CCC. 

For this 2013 document, these six studies and the data from the two additional studies 

summarized above, have been re-evaluated and re-considered for inclusion in deriving a new 

chronic criterion for ammonia in order to consider and include all available, reliable toxicity test 

information for this recreationally, commercially and ecologically important taxon. The data 

were re-examined with specific consideration of whether unbounded (greater or less than) values 

add relevant information to determination of final SMCVs for Oncorhynchus clarkii, O. mykiss, 

and O. nerka. A decision rule was developed for evaluating chronic values (EC20s) for potential 

use in deriving an SMCV for a salmon species. In developing the decision rule, it was noted that 

“greater than” values for concentrations of low magnitude, and “less than” values for 

concentrations of high magnitude do not add significant information to the analysis. That is, if a 

researcher only tested very low concentrations and found no chronic effects or very high 

concentrations and found 100% response for a chronic endpoint, those data do not significantly 

enhance understanding of the toxicity of ammonia. Conversely, if a researcher only tested very 

low concentrations and found significant chronic effects, indicating the test material was highly 

toxic, or relatively high concentrations and found incomplete response for a chronic endpoint, 

indicating low toxicity of the materials, those data do significantly enhance understanding of the 

toxicity of ammonia. Thus, the decision rule was applied as follows: “greater than” (>) low CVs
61

and “less than” (<) high CVs were not used in the calculation of the SMCV; but “less than” (<) 

low CVs and a “greater than” (>) high CVs were included in the SMCV.

Following this decision rule, the SMCV for O. clarkii is the normalized EC20 of 25.83 mg 

TAN/L from Koch et al. (1980). The SMCV for O. mykiss is 6.663 mg TAN/L at pH 7, which is 

the geometric mean of the <3.246 mg TAN/L value from Calamari et al. (1977, 1981), the 

<3.515 mg TAN/L value from Solbe and Shurben (1989), the >11.08 mg TAN/L value from 

Thurston et al. (1984b), and the 15.60 mg TAN/L value from Brinkman et al. (2009). With 

respect to the SMCV for O. mykiss, both the Calamari et al. (1977, 1981) and the Solbe and 

Shurben (1989) values are low “less than” values, indicating demonstrated toxicity at low 

concentrations of ammonia, while the Thurston et al. (1984b) value is a relatively high “greater 

than” value, indicating lower toxicity to O. mykiss in this test, compared to the Calamari (1977, 

1981) and Solbe and Shurben (1989) values with respect to the SMCV for O. mykiss. Finally, 

the SMCV for O. nerka is <10.09 mg TAN/L (Rankin 1979), and has been included as a 

relatively low “less than” value, indicating relative sensitivity to the effects of ammonia in this 

test. The <48 mg TAN/L value (at pH 7) from Thurston et al. (1978) re-calculated for O. clarkii

(see Appendix C; value represents the geometric mean of four values) and the <45.50 mg TAN/L

value from Burkhalter and Kaya (1977) for O. mykiss (retained in Appendix B) are not included 

in the SMCV calculations because they are high “less than” values, and do not add important

information to the analyses. The new GMCV for Oncorhynchus in this 2013 Update document 

is 12.02 mg TAN/L, which is the geometric mean of the three SMCVs for Oncorhynchus clarkii 

(25.83 mg TAN/L), O. mykiss (6.663 mg TAN/L), and O. nerka (<10.09 mg TAN/L) (Appendix 

B), resulting in Oncorhynchus as being seventh most sensitive GMCV (Table 4).

Another order of insect or a phylum not already represented: Minimum Data Requirement 

Number 8

For the MDR identified earlier as “#8,” “another order of insect or a phylum not already 

represented,” there are no additional chronic toxicity data for any freshwater animal that would 

fulfill this MDR in the chronic dataset (the acute dataset fulfills all eight MDRs). Therefore, 

EPA developed a surrogate ammonia CV for the Phylum Annelida by using the geometric mean 

acute value from the four available genera (Dendrocoelus, Limnodrilus, Lumbriculus, and 

Tubifex) and applying an ACR from other invertebrate groups. There is less than a factor of two 
62

difference between the GMAVs for the most (Dendrocoelus, 119.5 mg TAN/L) and least 

(Lumbriculus, 218.7 mg TAN/L) sensitive genus (see Table 3). A surrogate chronic value was

derived by dividing the GMAV for all four annelids (176.2 mg TAN/L) by a geometric mean 

species level invertebrate acute to chronic ratio (6.320), represented by pelagic crustaceans 

(cladocerans), a benthic crustacean (amphipod) and prosobranch snail (see Appendix F AcuteChronic Ratios). The resulting surrogate CV for Phylum Annelida is 27.88 mg TAN/L (at pH 7 

and 20°C).

Protection of Endangered Species

The dataset for ammonia is particularly extensive and includes data representing species 

that are Federally-listed as threatened or endangered by the U.S. Fish and Wildlife Service and/or 

NOAA National Marine Fisheries Service. Summaries are provided here describing the data for 

the listed species and demonstrating that the 2013 ammonia criteria update is protective of these 

species, based on best available scientific data.

Key acute toxicity data for listed species

The acute criterion dataset for ammonia now includes 12 aquatic species that are

Federally-listed as threatened, endangered or of concern. 

For unionid mussels, the 2013 criterion acute dataset includes acceptable data for 16 

freshwater species across 11 genera. Of these, five of the mussel species are Federally-listed as 

threatened or endangered (as identified in Table 3). The oyster mussel (Epioblasma 

capsaeformis) is a Federally-listed species and is the third most sensitive in the acute dataset 

with a GMAV, based on a single SMAV, of 31.14 mg TAN/L. The SMAV/2 for the oyster 

mussel is approximately 16 mg TAN/L, similar to the 2013 acute criterion value of 17 mg 

TAN/L. The SMAV/2 is a value considered statistically indistinguishable from control mortality 

or effect based on analysis of 219 acute toxicity tests on a range of chemicals, as described in the 

Federal Register on May 18, 1978 (43 FR 21506-18). Thus, the magnitude of acute effects to 

this species at the SMAV/2 are not expected to significantly impact the species, because it is 

expected to be statistically indistinguishable from effects to control (unexposed) organisms. 

Furthermore, the acute criterion specifies that this concentration should not be exceeded for more 

than one hour once every three years on average, providing further protection through the 
63

limitation of any excursions above the criterion. Thus, the 2013 recommended CMC for 

ammonia of 17 mg TAN/L should be protective of oyster mussels. In waters where this listed 

species is present, a site-specific criterion could be considered using the SMAV for that species 

as the FAV from which to derive the CMC.

The Lampsilis GMAV of 46.63 mg TAN/L reflects the geometric mean of SMAVs for 

six mussel species, two (L. abrupta and L. higginsii) of which are endangered and a third (L. 

rafinesqueana) that is a Federal species of concern (Table 3). The SMAVs for this genus range 

from 26.03 mg TAN/L (L. abrupta) to 69.97 mg TAN/L (L. rafinesqueana) (Appendix A). 

Given the range of sensitivity within this genus with listed species at both the most and least

sensitive ends of the range, the CMC of 17 mg TAN/L should be protective of the genus as a 

whole, with SMCVs/2 ranging from 13 to 34 mg TAN/L. Again, the acute criterion specifies 

that a concentration of 17 mg TAN/L should not be exceeded for more than one hour once every 

three years on average, providing further protection of species, through the limitation of any 

excursions above the criterion. In waters where the listed species are present, a site-specific 

criterion could be considered using the SMAV for that species as the FAV from which to derive 

the CMC.

Also among the ten most sensitive GMAVs in the acute dataset is the GMAV for the 

endangered Lost River sucker (Deltistes luxatis) endemic to the Klamath Basin of northern 

California and southern Oregon (Appendix A). The reported LC50s at test temperature 20°C and 

pH 8.0 were 10.35 and 16.81 mg TAN/L for larval and juvenile fish, expressed as total ammonia 

(Appendix A). The LC50s normalized to pH 7 and 20°C are 44.42 and 72.18 mg TAN/L, 

respectively (Appendix A). The GMAV for Lost River sucker is calculated as the geometric 

mean of the two normalized LC50s, or 56.62 mg TAN/L (Table 3), with an SMAV/2, or expected 

low mortality level, of approximately 28 mg TAN/L, significantly above the CMC. Lost River 

sucker represents the ninth most sensitive genus in the acute dataset, and second most sensitive 

fish species (following mountain whitefish which is the most sensitive fish GMAV), and thus is 

expected to be protected by the CMC of 17 mg TAN/L.

The second most acutely sensitive salmonid genus (after Prosopium, represented by the

mountain whitefish, Prosopium williamsoni, acute sensitivity rank 8) is Oncorhynchus, 

represented by data for six different species, three of which are threatened or endangered, with 

SMAVs ranging from 78.92 mg TAN/L for Cutthroat trout, O. clarkii, to 180.7 mg TAN/L for 
64

pink salmon, O. gorbuscha. The GMAV for Oncorhynchus (99.15 mg TAN/L) is ranked #25 in

acute sensitivity (Table 3). All SMAV/2 values for the threatened or endangered species tested 

in this genus are significantly above the acute criterion magnitude. Thus, the acute criterion is 

expected to be protective of threatened and endangered salmonid species.

Key chronic toxicity data for listed species

In the chronic dataset for ammonia, the Federally-listed species are represented by three 

salmonid species in the genus Oncorhynchus, including sockeye salmon, rainbow trout, and the 

subspecies Lahontan cutthroat trout. The GMCV for Oncorhynchus of 12.02 mg TAN/L

includes the three SMCVs ranging from 6.663 (rainbow trout) to 25.83 mg TAN/L (Lahontan 

cutthroat trout) (Table 4). The CCC for ammonia of 1.9 mg TAN/L is expected to be protective 

of this genus as a whole. At pH 7, the CCC is 3.5 times lower than the chronic value for the 

most sensitive tested listed salmonid species, O. mykiss, which includes populations of rainbow 

trout and steelhead trout.

In addition, three other studies provide useful information with which to assess the 

protectiveness of the CCC for threatened and endangered fish species (data included in Appendix 

C). All three studies indicate that the chronic criterion is expected to be protective of the 

endangered or listed species tested by the researchers, as described below.

Meyer and Hansen (2002) conducted a 30-day toxicity test with late-stage larvae (0.059 

g) of Lost River suckers (Deltistes luxatus) at pH 9.5. The exposure duration and pH were 

chosen to represent the period of combined elevated unionized ammonia concentrations and 

elevated pH that occur during cyanobacterial blooms in surface waters of Upper Klamath Lake, 

which have been shown to last for several weeks to a month. Survival decreased significantly at 

1.23 and 2.27 mg TAN/L, whereas the highest NOEC for all endpoints (survival, growth, body 

ions, and swimming performance) was 0.64 mg TAN/L. Control survival was > 90 percent. The 

calculated LOEC of 1.23 mg TAN/L at test pH and temperature when normalized to pH 7

corresponds to a value of 25.31 mg TAN/L, again, substantially higher than the 2013 chronic 

criterion value (Appendix C).

In order to determine if whole effluent toxicity testing is protective of threatened and 

endangered fish species, Dwyer et al. (2005) conducted 7-day chronic toxicity tests with 

Ceriodaphnia dubia (neonates, <24 h old) and fathead minnow larvae (Pimephales promelas, 
65

<24 h) in addition to the following six threatened and endangered fish species: bonytail chub 

(Gila elegans), spotfin chub (Erimonax, formerly Cyprinella, monachus), Cape Fear shiner 

(Notropis mekistocholas), gila topminnow (Poeciliopsis occidentalis), Colorado pikeminnow 

(Ptychocheilus lucius), and razorback sucker (Xyrauchen texanus). The age of the six threatened 

and endangered fish species used during the 7-day ammonia exposures ranged from <1 to 7 days. 

The combined effect on test species survival and growth were determined as EC25 values. The 

six endangered species, presented in the same order as they are listed above, have reported EC25

values of: 11.0, 15.8, 8.80, 24.1, 8.90 and 13.4 mg TAN/L; or 23.24, 33.37, 18.59, 50.91, 18.80

and 28.30 mg TAN/L when adjusted to a pH of 7.0 (Appendix C). These values are all 

substantially higher than the 2013 chronic criterion concentration value of 1.9 mg TAN/L. 

Based on the results, the two species typically used for whole effluent toxicity testing (C. dubia 

and P. promelas) were more sensitive to ammonia and are protective of the six listed fish species 

when used as surrogate test species. 

Fairchild et al. (2005) conducted 28-day toxicity tests with early life stages of Colorado 

pikeminnow (Ptychocheilus lucius) and razorback sucker (Xyrauchen texanus), and compared 

the results of those tests with a test using a surrogate fish species, the fathead minnow 

(Pimephales promelas). Effect concentrations based on the survival and growth endpoints of the 

fathead minnow and razorback sucker tests were not different; however, growth was the more 

sensitive endpoint for the Colorado pikeminnow test. The 28-day growth LOEC for the 

Colorado pikeminnow was 8.60 mg TAN/L, or 29.75 mg TAN/L at pH 7, substantially greater 

than the 2013 chronic criterion. The 28-day survival LOEC for the razorback sucker was 13.25 

mg TAN/L, or 46.58 mg TAN/L at pH 7. Both endangered fish species exhibited similar 

sensitivity to ammonia as the fathead minnow (LOEC of 32.71 mg TAN/L at pH 7; see 

Appendix C). The same can be said for the Lost River sucker, which indicates that these 

particular endangered fish species are expected to be protected by the CCC value calculated in 

this 2013 AWQC Update.

Comparison of 1999, 2009, and 2013 Criteria Values

Table 8 provides a comparison of the four most sensitive taxa used to calculate the CCC 

in this 2013 AWQC Update document compared to the four most sensitive taxa used to calculate 

the CCC in the 1999 AWQC document.
66

The 2013 CCC is about twice the magnitude of the draft 2009 CCC recommended for 

waters with mussels present (1.9 vs. 0.91 mg TAN/L, respectively, at pH 7, T=20°C) as a result 

of differences in the data used in the CCC derivations. Based on a new study by Wang et al. 

(2011) described in the Effects Analysis section under Summaries of Studies Used in Chronic 

Criterion Determination, pg. 34, above, the lowest GMCV for the mussel genus Lampsilis

increased from 1.154 mg TAN/L in the 2009 draft AWQC to 2.216 mg TAN/L in the 2013 

AWQC. As a result, compared to the four lowest GMCVs in the 2009 draft CCC, the four 

lowest GMCVs in the 2013 CCC have a smaller range of variation in values (2.216 to 7.547 mg 

TAN/L) which decreases the uncertainty of the 5th percentile GMCV estimation. Also in the 

2009 draft CCC, there were only 13 GMCVs in the dataset used to derive the CCC while in the 

2013 CCC, there are 16 GMCVs used to derive the CCC, because of the addition of the GMCVs 

for Hyalella azteca, the insect Pteronarcella badia, and salmonids (Oncorhynchus spp.). The 

new GMCVs affect the chronic species sensitivity distribution. The cumulative probability (P) 

decreases as a function of the increased number of GMCVs and results in an increase in the 

FCV.
67

Table 8. Comparison of the Four Taxa Used to Calculate the FCV and CCC in the 1999 Update, 2009 Draft and the 2013 

AWQC.

1999 Update CCC Magnitude 2009 Draft Update CCC Magnitude 2013 Final CCC Magnitude

Species

pH 8.0,

T=25°C

(mg 

TAN/L)

pH 7.0,

T=20°C

(mg 

TAN/L) Species

pH 8.0,

T=25°C

(mg 

TAN/L)

pH 7.0,

T=20°C

(mg 

TAN/L) Species

pH 7.0,

T=20°C

(mg 

TAN/L)

Fathead minnow, 

Pimephales promelas 3.09 7.503 Long fingernailclam, Musculium transversum <2.260 7.552 Long fingernailclam, Musculium transversum 7.547

Lepomis sp. 

(Centrarchidae), includes: 

Bluegill sunfish, 

L. macrochirus, and 

Green sunfish, 

L. cyanellus

2.85 6.92

Lepomis sp. 

(Centrarchidae), includes: 

Bluegill sunfish, 

L. macrochirus, and 

Green sunfish, 

L. cyanellus

2.852 6.924

Lepomis sp. 

(Centrarchidae), includes: 

Bluegill sunfish, 

L. macrochirus, and 

Green sunfish, 

L. cyanellus

6.92

Long fingernailclam, 

Musculium transversum <2.26 7.547 Rainbow mussel,Villosa iris <0.9805 3.286 Rainbow mussel,Villosa iris 3.501

Amphipod, 

Hyalella azteca <1.45 4.865

Lampsilis sp. 

(Unionidae), includes: 

Wavy-rayed lamp mussel, 

L. fasciola and 

Fatmucket, L. siliquoidea

<0.3443 1.154

Lampsilis sp. 

(Unionidae), includes: 

Wavy-rayed lamp mussel, 

L. fasciola and 

Fatmucket, L. siliquoidea

2.216

CCC 1.2 4.5 CCC 0.26 0.91 CCC 1.9
68

Comparison of statistical approaches to develop the chronic criterion: EC20 vs. MATC

In this 2013 ammonia criteria update, the CCC is based on a 20 percent reduction in 

survival, growth, or reproduction, which is a risk management decision made by EPA in 1999 

and also retained for this document. When an EC20 was not provided in a study, the EPA’s 

TRAP program was used to estimate the EC20 as the basis for the GMCV and included the 

resultant CCC derivation of 1.9 mg TAN/L. An alternative chronic measure of effect that is 

commonly used is the MATC, which is the geometric mean of the NOEC and LOEC. In the case 

of the current ammonia dataset, using MATCs to derive the chronic criteria would result in an 

FCV of 1.972 and CCC of 2.0 mg TAN/L. This comparison demonstrates that, for the current 

ammonia chronic dataset, the use of TRAP to estimate EC20 values does not result in a 

significant difference from the MATC, another statistical approach frequently used to develop 

chronic effects assessments and criteria.

The concentrations of TAN affecting freshwater animals in this 2013 AWQC update are 

normalized to pH 7.0 for all aquatic organisms and 20°C for invertebrates. In contrast, the 

concentrations of TAN affecting freshwater animals in the 1999 AWQC were normalized to pH 

8.0 for all organisms and temperature 25°C for invertebrates. The current pH (7) and 

temperature (20°C) used are considered to more closely reflect ambient pH and temperatures 

found generally in surface waters in the U.S. The acute and chronic criterion values can be 

adjusted to reflect local pH and temperature using the values in Tables 5a, 5b, and 6 derived 

from the equations presented in The National Criteria for Ammonia in Fresh Water section 

(pages 40-49). 

UNUSED DATA

For this 2013 criteria update document, EPA considered and evaluated all available data 

that could possibly be used to derive the new acute and chronic criteria for ammonia in fresh 

water. A substantial amount of those data were associated with studies that did not meet the 

basic QA/QC requirements described in the 1985 Guidelines (see Stephan et al. 1985). In such 

cases, EPA further scrutinized those studies where either: (1) the study included tests with a 

species associated with one of the four most sensitive GMAVs or GMCVs used to derive the 

2013 criterion; or (2) the study provided results of tests where the normalized acute or chronic 
69

value for the test was within a factor of approximately two of the fourth ranked most sensitive 

GMAV or GMCV, and thus might be considered potentially influential to the acute or chronic 

criterion. For each study that was potentially influential, but did not meet the additional data 

quality requirements for its use in deriving criteria for ammonia, the study and its results were

included in Appendix J (acute studies) and K (chronic studies), and a rationale is provided for its 

exclusion. A list of all other studies considered but removed from consideration for use in 

deriving the criteria is provided in Appendix L with a code (and in some cases comments) 

indicating the reason(s) for exclusion.
70

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http://minerals.usgs.gov/minerals/pubs/commodity/nitrogen/nitromcs07.pdf.

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86

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals.

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Insect (8th-10th instar),

Erythromma najas

Ammonium 

chloride 4 d R,U 7.5 25 589 1618 Beketov 2002

Insect (8th-10th instar),

Erythromma najas

Ammonium 

chloride 4 d R,U 8.7 25 168 4163 Beketov 2002

Insect (8th-10th instar),

Erythromma najas

Ammonium 

chloride 4 d R,U 9.1 25 49.2 2361 2515 2515 Beketov 2002

Caddisfly,

Philarctus quaeris

Ammonium 

chloride 4 d F,M 7.8 21.9 296.5 1032 Arthur et al. 1987

Caddisfly,

Philarctus quaeris

Ammonium 

chloride 4 d F,M 7.8 13.3 561.7 958.4 994.5 994.5 West 1985; Arthur et al. 1987

Beetle,

Stenelmis sexlineata

Ammonium 

chloride 4 d F,M 8.7 25 29.7 735.9 735.9 735.9 Hazel et al. 1979

Crayfish,

Orconectes immunis

Ammonium 

chloride 4 d F,M 7.9 17.1 488.1 1367 Arthur et al. 1987

Crayfish (adult),

Orconectes immunis

Ammonium 

chloride 4 d F,M 8.2 4.6 999.4 1757 1550 West 1985; Arthur et al. 1987

Crayfish (2.78 cm),

Orconectes nais

Ammonium 

chloride 4 d F,M 8.3 26.5 23.15 303.8 303.8 686.2 Evans 1979

Midge (10 d old, 2-3 instar),

Chironomus riparius

Ammonium 

chloride 4 d R,M 7.7 21.7 357.7 1029 1029 Monda et al. 1995 

Midge,

Chironomus tentans

Ammonium 

chloride 4 d S,M 6.69 23 430 443.0 Besser et al. 1998

Midge,

Chironomus tentans

Ammonium 

chloride 4 d S,M 7.56 23 564 1439 Besser et al. 1998

Midge (2nd instar),

Chironomus tentans

Ammonium 

chloride 4 d F,M 6.5 25 371 415.1 Schubauer-Berigan et al. 1995
87

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Midge (2nd instar),

Chironomus tentans

Ammonium 

chloride 4 d F,M 8.1 25 78.1 614.0 Schubauer-Berigan et al. 1995

Midge (2nd instar),

Chironomus tentans

Ammonium 

chloride 4 d F,M 6.5 25 368 411.7 Schubauer-Berigan et al. 1995

Midge (2nd instar),

Chironomus tentans

Ammonium 

chloride 4 d F,M 8.1 25 50.5 397.0 451.8 681.8 Schubauer-Berigan et al. 1995

Mayfly (middle to late instar),

Drunella grandis

Ammonium 

chloride 4 d F,M 7.84 12.8 259.1 455.5 Thurston et al. 1984b

Mayfly (middle to late instar),

Drunella grandis

Ammonium 

chloride 4 d F,M 7.84 13.2 195.6 355.6 Thurston et al. 1984b

Mayfly (middle to late instar),

Drunella grandis

Ammonium 

chloride 4 d F,M 7.85 12 319 534.5 442.4 442.4 Thurston et al. 1984b

Aquatic sowbug,

Caecidotea racovitzai

(previously Asellus racovitzai)

Ammonium 

chloride 4 d F,M 7.8 22 148.8 522.3 Arthur et al. 1987

Aquatic sowbug (adult),

Caecidotea racovitzai

Ammonium 

chloride 4 d F,M 8 4 357.8 407.7 West 1985; Arthur et al. 1987

Aquatic sowbug,

Caecidotea racovitzai

Ammonium 

chloride 4 d F,M 7.81 11.9 176 272.2 387.0 387.0 Thurston et al. 1983

Isopod (adult),

Asellus aquaticus

Ammonium 

chloride 4 d F,M 7.05 12 2.60 575.2 Dehedin et al. 2012

Isopod (adult),

Asellus aquaticus

Ammonium 

chloride 4 d F,M 7.05 12 1.25 276.6 Dehedin et al. 2012

Isopod (adult),

Asellus aquaticus

Ammonium 

chloride 4 d F,M 7.05 12 1.70 376.1 Dehedin et al. 2012

Isopod (adult),

Asellus aquaticus

Ammonium 

chloride 4 d F,M 7.05 18 2.61 603.8 Dehedin et al. 2012

Isopod (adult),

Asellus aquaticus

Ammonium 

chloride 4 d F,M 7.05 18 1.40 323.9 Dehedin et al. 2012

Isopod (adult),

Asellus aquaticus

Ammonium 

chloride 4 d F,M 7.05 18 1.95 451.1 Dehedin et al. 2012

Isopod (adult),

Asellus aquaticus

Ammonium 

chloride 4 d F,M 7.05 24 1.00 246.6 Dehedin et al. 2012
88

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Isopod (adult),

Asellus aquaticus

Ammonium 

chloride 4 d F,M 7.05 24 1.00 246.6 Dehedin et al. 2012

Isopod (adult),

Asellus aquaticus

Ammonium 

chloride 4 d F,M 7.05 24 2.00 493.1 378.2 378.2 Dehedin et al. 2012

Threespine stickleback

(juvenile-adult, 32-60 mm),

Gasterosteus aculeatus

Ammonium 

chloride 4 d S,M 7.1 23.3 198.1 216.5 Hazel et al. 1971

Threespine stickleback

(juvenile-adult, 32-60 mm),

Gasterosteus aculeatus

Ammonium 

chloride 4 d S,M 7.15 15 577 667.4 Hazel et al. 1971

Threespine stickleback

(juvenile-adult, 32-60 mm),

Gasterosteus aculeatus

Ammonium 

chloride 4 d S,M 7.25 23.3 203.8 264.0 Hazel et al. 1971

Threespine stickleback

(juvenile-adult, 32-60 mm),

Gasterosteus aculeatus

Ammonium 

chloride 4 d S,M 7.5 15 143.9 261.1 Hazel et al. 1971

Threespine stickleback

(juvenile-adult, 32-60 mm),

Gasterosteus aculeatus

Ammonium 

chloride 4 d S,M 7.5 23.3 78.7 142.8 Hazel et al. 1971

Threespine stickleback

(juvenile-adult, 32-60 mm),

Gasterosteus aculeatus

Ammonium 

chloride 4 d S,M 7.5 23.3 115.4 209.5 Hazel et al. 1971

Threespine stickleback

(juvenile-adult, 32-60 mm),

Gasterosteus aculeatus

Ammonium 

chloride 4 d S,M 7.5 15 259 470.0 281.5 281.5 Hazel et al. 1971

Mayfly,

Callibaetis skokianus

Ammonium 

chloride 4 d F,M 7.7 10.8 263.5 307.2 Arthur et al. 1987

Mayfly,

Callibaetis skokianus

Ammonium 

chloride 4 d F,M 7.9 13.3 211.7 432.7 364.6 West 1985; Arthur et al. 1987

Mayfly (middle to late instar),

Callibaetis sp.

Ammonium 

chloride 4 d F,M 7.81 11.9 107.8 166.7 166.7 246.5 Thurston et al. 1984b
89

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Dragonfly (<233 d old),

Pachydiplax longipennis

Ammonium 

chloride 4 d F,M 8 12 76.92 170.1 Diamond et al. 1993

Dragonfly (<140 d old),

Pachydiplax longipennis

Ammonium 

chloride 4 d F,M 8 20 74.37 319.2 233.0 233.0 Diamond et al. 1993

Mottled sculpin (1.8 g, 5.4 cm),

Cottus bairdii

Ammonium 

chloride 4 d F,M 8.02 12.4 49.83 222.2 222.2 222.2 Thurston and Russo 1981

Western mosquitofish,

Gambusia affinis - 4 d S,U 7.75 19 129.6 352.9 Wallen et al. 1957

Western mosquitofish,

Gambusia affinis - 4 d S,U 8.2 19.5 34.54 217.7 Wallen et al. 1957

Western mosquitofish,

Gambusia affinis - 4 d S,U 8.5 23 14.64 165.0 Wallen et al. 1957

Western mosquitofish,

Gambusia affinis - 4 d S,U 8 24 42.53 182.6 219.3 219.3 Wallen et al. 1957

Oligochaete worm,

Lumbriculus variegatus

Ammonium 

chloride 4 d S,M 7.56 23 286 729.5 Besser et al. 1998

Oligochaete worm,

Lumbriculus variegatus

Ammonium 

chloride 4 d S,M 6.69 23 302 311.1 Besser et al. 1998

Oligochaete worm (10-25 mm),

Lumbriculus variegatus

Ammonium 

chloride 4 d R,M 8.2 15 13.66 56.88 Hickey and Vickers 1994

Oligochaete worm (adult),

Lumbriculus variegatus - 4 d F,M 6.5 25 100 111.9 Schubauer-Berigan et al. 1995

Oligochaete worm (adult),

Lumbriculus variegatus - 4 d F,M 6.5 25 200 223.8 Schubauer-Berigan et al. 1995

Oligochaete worm (adult),

Lumbriculus variegatus - 4 d F,M 8.1 25 34 267.3 Schubauer-Berigan et al. 1995

Oligochaete worm (adult),

Lumbriculus variegatus - 4 d F,M 8.1 25 43.5 342.0 218.7 218.7 Schubauer-Berigan et al. 1995

Tubificid worm,

Tubifex tubifex

Ammonium 

chloride 4 d S,U 8.2 12 66.67 216.5 216.5 216.5 Stammer 1953
90

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Marsh ramshorn snail,

Planorbella trivolvis

(previously Helisoma trivolvis)

Ammonium 

chloride 4 d F,M 7.9 22 47.73 200.7 Arthur et al. 1987

Marsh ramshorn snail,

Planorbella trivolvis

Ammonium 

chloride 4 d F,M 8.2 12.9 63.73 223.0 211.6 211.6 Arthur et al. 1987

Scud (7-14 d old),

Hyalella azteca

Ammonium 

chloride 4 d R,M 8.3 25 39.8 461.2 Ankley et al. 1995

Scud (7-14 d old),

Hyalella azteca

Ammonium 

chloride 4 d R,M 7.31 25 64 135.1 Ankley et al. 1995

Scud (7-14 d old),

Hyalella azteca

Ammonium 

chloride 4 d R,M 6.43 25 105 114.6 192.6 192.6 Ankley et al. 1995

Stonefly, Little golden stonefly

(middle to late instar),

Skwala americana

Ammonium 

chloride 4 d F,M 7.81 13.1 109.3 186.7 Thurston et al. 1984b

Stonefly, Little golden stonefly

(middle to late instar),

Skwala americana

Ammonium 

chloride 4 d F,M 7.76 13.8 119.6 198.3 192.4 192.4 Thurston et al. 1984b

Mozambique tilapia (juvenile),

Oreochromis mossambicus

Ammonium 

chloride 4 d R,U 7.2 28 151.5 185.2 185.2 185.2 Rani et al. 1998

Amphipod (4-6 mm),

Crangonyx pseudogracilis

Ammonium 

chloride 4 d S,U 7.5 12 43.36 40.54 Prenter et al. 2004

Amphipod,

Crangonyx pseudogracilis

Ammonium 

chloride 4 d F,M 8 4 199.5 227.3 West 1985; Arthur et al. 1987

Amphipod,

Crangonyx pseudogracilis

Ammonium 

chloride 4 d F,M 8 12.1 216 481.7 West 1985; Arthur et al. 1987

Amphipod,

Crangonyx pseudogracilis

Ammonium 

chloride 4 d F,M 8 13.3 115.3 284.1 West 1985; Arthur et al. 1987

Amphipod,

Crangonyx pseudogracilis

Ammonium 

chloride 4 d F,M 8 24.9 25.1 161.7 West 1985; Arthur et al. 1987

Amphipod,

Crangonyx pseudogracilis

Ammonium 

chloride 4 d F,M 8.2 13 81.6 287.9 270.5 West 1985; Arthur et al.1987
91

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Amphipod (13 d),

Crangonyx sp.

Ammonium 

chloride 4 d F,M 8 12 79.23 175.3 Diamond et al. 1993

Amphipod (8-42 d),

Crangonyx sp.

Ammonium 

chloride 4 d F,M 8 20 19.83 85.13 122.2 181.8 Diamond et al. 1993

Tubificid worm (30-40 mm),

Limnodrilus hoffmeisteri - 4 d F,M 7.9 11.5 96.62 170.2 170.2 170.2 Williams et al. 1986

Pouch snail,

Physa gyrina

Ammonium 

chloride 4 d F,M 8 4 114.9 131.0 West 1985; Arthur et al. 1987

Pouch snail,

Physa gyrina

Ammonium 

chloride 4 d F,M 8.2 5.5 85.13 161.3 West 1985; Arthur et al. 1987

Pouch snail,

Physa gyrina

Ammonium 

chloride 4 d F,M 8.1 12.1 76.29 205.9 West 1985; Arthur et al. 1987

Pouch snail,

Physa gyrina

Ammonium 

chloride 4 d F,M 8.2 12.8 50.25 174.4 West 1985; Arthur et al. 1987

Pouch snail,

Physa gyrina

Ammonium 

chloride 4 d F,M 8 13.3 62.39 153.7 West 1985; Arthur et al. 1987

Pouch snail,

Physa gyrina

Ammonium 

chloride 4 d F,M 8 24.9 26.33 169.7 164.5 164.5 West 1985; Arthur et al. 1987

Damselfly (8-10 mm),

Enallagma sp.

- 4 d F,M 7.9 11.5 93.1 164.0 164.0 164.0 Williams et al. 1986

Water flea (<24 hr),

Chydorus sphaericus

Ammonium 

chloride 4 d S,M 8 20 37.88 162.6 162.6 162.6 Dekker et al. 2006

Fathead minnow (larva, 14 d),

Pimephales promelas - 4 d S,U 7.6 20 37.56 79.59 Markle et al. 2000

Fathead minnow,

Pimephales promelas

Ammonium 

chloride 4 d S,M 7.52 20.25 36.73 68.17 EA Engineering 1985

Fathead minnow,

Pimephales promelas

Ammonium 

chloride 4 d S,M 7.48 19.85 40.93 72.10 EA Engineering 1985

Fathead minnow,

Pimephales promelas

Ammonium 

chloride 4 d S,M 7.52 20.25 37.49 69.59 EA Engineering 1985
92

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Fathead minnow,

Pimephales promelas

Ammonium 

chloride 4 d S,M 7.48 19.85 41.79 73.61 EA Engineering 1985

Fathead minnow,

Pimephales promelas

Ammonium 

chloride 4 d S,M 7.48 19.85 43.49 76.61 EA Engineering 1985

Fathead minnow (4-6 d old),

Pimephales promelas

Ammonium 

chloride 4 d R,M 8.01 25 14.4 63.00 Buhl 2002

Fathead minnow,

Pimephales promelas

Ammonium 

chloride 4 d R,M 8 20 5.389 23.13 Diamond et al. 1993

Fathead minnow,

Pimephales promelas

Ammonium 

chloride 4 d R,M 8 20 6.1 26.19 Diamond et al. 1993

Fathead minnow (1.9 g),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.9 3.4 229.7 818.4 West 1985; Arthur et al. 1987

Fathead minnow (1.8 g),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.1 12.1 56.07 291.3 West 1985; Arthur et al. 1987

Fathead minnow (1.6 g),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8 17.1 52.22 224.2 West 1985; Arthur et al. 1987

Fathead minnow (1.7 g),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.1 26.1 29.23 151.8 West 1985; Arthur et al. 1987

Fathead minnow,

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.05 14 47.29 223.2 DeGraeve et al. 1980

Fathead minnow (4-5 mo),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.46 6 97.27 166.4 DeGraeve et al. 1987

Fathead minnow (4-5 mo),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.46 10 101.7 174.0 DeGraeve et al. 1987

Fathead minnow (4-5 mo),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.41 15 76.58 122.0 DeGraeve et al. 1987

Fathead minnow (4-5 mo),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.41 20 78.22 124.6 DeGraeve et al. 1987

Fathead minnow (4-5 mo),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.45 20 66.94 112.9 DeGraeve et al. 1987

Fathead minnow (4-5 mo),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.4 25 81.81 128.5 DeGraeve et al. 1987

Fathead minnow (4-5 mo),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.41 25 91.4 145.6 DeGraeve et al. 1987

Fathead minnow (4-5 mo),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.44 30 64.12 106.6 DeGraeve et al. 1987
93

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Fathead minnow

(0.28 g, 26.6 mm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.14 22 25.16 141.2 Mayes et al. 1986

Fathead minnow

(10 mm length),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.9 20.6 28.9 103.0 Nimmo et al. 1989

Fathead minnow (10 mm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.2 6.2 7.322 46.15 Nimmo et al. 1989

Fathead minnow (10 mm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.8 20.1 18.73 55.68 Nimmo et al. 1989

Fathead minnow (10 mm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.8 19.8 32.12 95.49 Nimmo et al. 1989

Fathead minnow (25 mm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.1 19.6 24.89 129.3 Nimmo et al. 1989

Fathead minnow (25 mm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.2 6.2 11.56 72.86 Nimmo et al. 1989

Fathead minnow (25 mm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.1 5.8 19.94 103.6 Nimmo et al. 1989

Fathead minnow (25 mm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.1 5.8 21.44 111.4 Nimmo et al. 1989

Fathead minnow (25 mm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.7 20.1 32.25 80.61 Nimmo et al. 1989

Fathead minnow

(15 mm, 0.0301 g),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.46 4.1 18.54 193.5 Reinbold and Pescitelli 1982b

Fathead minnow

(16 mm, 0.0315 g),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.02 23.9 19.55 87.16 Reinbold and Pescitelli 1982b

Fathead minnow

(19 mm, 0.0629 g),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.26 4.6 30.57 216.5 Reinbold and Pescitelli 1982b

Fathead minnow

(21 mm, 0.0662 g),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.16 25.2 17.65 102.9 Reinbold and Pescitelli 1982b
94

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Fathead minnow

(5.2 cm, 1.1 g),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.7 21.65 63.02 157.5 Sparks 1975

Fathead minnow (0.2 g),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.78 25.9 40.85 117.3 Swigert and Spacie 1983

Fathead minnow (0.5 g),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.8 25.6 42.65 126.8 Swigert and Spacie 1983

Fathead minnow

(1.9 g, 5.2 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.83 11.8 45.71 143.4 Thurston et al. 1981c

Fathead minnow

(1.9 g, 5.2 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.82 12 62.72 193.3 Thurston et al. 1981c

Fathead minnow

(1.9 g, 5.2 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 6.51 13 260 192.9 Thurston et al. 1981c

Fathead minnow

(1.9 g, 5.2 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 9.03 13.2 5.94 169.6 Thurston et al. 1981c

Fathead minnow

(1.9 g, 5.2 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.51 13.5 18.88 216.9 Thurston et al. 1981c

Fathead minnow

(1.9 g, 5.2 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.01 13.8 145.9 147.2 Thurston et al. 1981c

Fathead minnow

(0.09 g, 2.0 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.91 16.3 51.55 187.1 Thurston et al. 1983

Fathead minnow

(0.09 g, 2.1 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.89 13.1 50.2 175.6 Thurston et al. 1983

Fathead minnow

(0.13 g, 2.3 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.64 13.6 58.4 132.1 Thurston et al. 1983
95

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Fathead minnow

(0.19 g, 2.6 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.68 13.5 64.7 156.3 Thurston et al. 1983

Fathead minnow

(0.22 g, 2.7 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.03 22.1 47.6 216.3 Thurston et al. 1983

Fathead minnow

(0.22 g, 2.9 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.06 22 42.6 205.0 Thurston et al. 1983

Fathead minnow

(0.26 g, 3.0 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.67 13.9 58.8 139.7 Thurston et al. 1983

Fathead minnow

(0.31 g, 3.0 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.05 13 74.65 352.4 Thurston et al. 1983

Fathead minnow

(0.31 g, 3.1 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.05 13.6 66.48 313.8 Thurston et al. 1983

Fathead minnow

(0.35 g, 3.1 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.94 19.1 42.3 162.3 Thurston et al. 1983

Fathead minnow

(0.42 g, 3.0 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.76 19 50.28 139.3 Thurston et al. 1983

Fathead minnow

(0.42 g, 3.6 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.66 13.4 58.2 136.0 Thurston et al. 1983

Fathead minnow

(0.47 g, 3.2 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.87 15.8 58.91 198.7 Thurston et al. 1983

Fathead minnow

(0.47 g, 3.2 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.83 22 50.6 158.7 Thurston et al. 1983

Fathead minnow

(0.5 g, 3.8 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.91 18.9 49.3 178.9 Thurston et al. 1983
96

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Fathead minnow

(0.8 g, 4.2 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.77 14.3 66.7 188.1 Thurston et al. 1983

Fathead minnow

(1.0 g, 4.6 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.77 14.1 72.71 205.1 Thurston et al. 1983

Fathead minnow

(1.4 g, 4.9 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.04 22.4 36.59 169.5 Thurston et al. 1983

Fathead minnow

(1.4 g, 5.0 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.08 21.4 44.8 224.0 Thurston et al. 1983

Fathead minnow

(1.4 g, 5.0 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 8.16 21.4 47.39 276.4 Thurston et al. 1983

Fathead minnow

(1.4 g, 5.1 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.88 21.7 50.9 174.8 Thurston et al. 1983

Fathead minnow

(1.4 g, 5.4 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.68 12.9 91.8 221.8 Thurston et al. 1983

Fathead minnow

(1.4 g, 5.5 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.63 13.2 89.85 199.9 Thurston et al. 1983

Fathead minnow

(1.5 g, 5.6 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.76 12.9 107.5 298.0 Thurston et al. 1983

Fathead minnow

(1.7 g, 5.2 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.84 21.7 55.43 177.0 Thurston et al. 1983

Fathead minnow

(2.1 g, 6.1 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.76 13.1 66.73 184.9 Thurston et al. 1983

Fathead minnow

(2.2 g, 6.2 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.74 12.8 52.2 139.7 Thurston et al. 1983
97

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Fathead minnow

(2.3 g, 6.3 cm),

Pimephales promelas

Ammonium 

chloride 4 d F,M 7.91 15.9 47.43 172.1 159.2 159.2 Thurston et al. 1983

Brook trout (3.12 g, 7.2 cm),

Salvelinus fontinalis

Ammonium 

chloride 4 d F,U 7.86 13.6 45.21 149.7 Thurston and Meyn 1984

Brook trout (3.40 g, 7.4 cm),

Salvelinus fontinalis

Ammonium 

chloride 4 d F,U 7.83 13.8 52.03 163.2 156.3 Thurston and Meyn 1984

Lake trout, siscowet (0.9 g),

Salvelinus namaycush

Ammonium 

chloride 4 d S,M 7.45 8.5 90.43 152.5 Soderberg and Meade 1992

Lake trout, siscowet (0.9 g),

Salvelinus namaycush

Ammonium 

chloride 4 d S,M 7.45 8.5 110.2 185.9 Soderberg and Meade 1992

Lake trout, siscowet (8 g),

Salvelinus namaycush

Ammonium 

chloride 4 d S,M 7.45 8.5 96.25 162.3 Soderberg and Meade 1992

Lake trout, siscowet (8 g),

Salvelinus namaycush

Ammonium 

chloride 4 d S,M 7.45 8.5 83.11 140.1 159.3 157.8 Soderberg and Meade 1992

Shortnose sturgeon (fingerling),

Acipenser brevirostrum

Ammonium 

chloride 4 d S,M 7.05 18 149.8 156.7 156.7 156.7 Fontenot et al. 1998

White sucker (5.6 g),

Catostomus commersonii

Ammonium 

chloride 4 d F,M 7.8 3.6 89.57 266.3 West 1985; Arthur et al. 1987

White sucker (5.2 g),

Catostomus commersonii

Ammonium 

chloride 4 d F,M 8.1 11.3 60.86 316.1 West 1985; Arthur et al. 1987

White sucker (12.6 g),

Catostomus commersonii

Ammonium 

chloride 4 d F,M 8.2 12.6 40.85 257.4 West 1985; Arthur et al. 1987

White sucker (9.6 g),

Catostomus commersonii

Ammonium 

chloride 4 d F,M 8.2 15.3 43.01 271.0 West 1985; Arthur et al. 1987

White sucker (110 mm),

Catostomus commersonii

Ammonium 

chloride 4 d F,M 7.8 20.2 31.21 92.80 Nimmo et al. 1989

White sucker (110 mm),

Catostomus commersonii

Ammonium 

chloride 4 d F,M 7.8 20.2 18.93 56.28 Nimmo et al. 1989

White sucker (92 mm, 6.3 g),

Catostomus commersonii

Ammonium 

chloride 4 d F,M 8.16 15 30.28 176.6 Reinbold and Pescitelli 1982c
98

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

White sucker (92 mm, 6.3 g),

Catostomus commersonii

Ammonium 

chloride 4 d F,M 8.14 15.4 29.65 166.3 Reinbold and Pescitelli 1982c

White sucker (11.4 g),

Catostomus commersonii

Ammonium 

chloride 4 d F,M 7.8 22.5 22.3 66.32 157.5 Swigert and Spacie 1983

Mountain sucker

(63.3 g, 18.2 cm),

Catostomus platyrhynchus

Ammonium 

chloride 4 d F,U 7.67 12 66.91 159.0 Thurston and Meyn 1984

Mountain sucker

(45.3 g, 16.2 cm),

Catostomus platyrhynchus

Ammonium 

chloride 4 d F,U 7.69 13.2 47.59 117.0 Thurston and Meyn 1984

Mountain sucker

(47.8 g, 15.9 cm),

Catostomus platyrhynchus

Ammonium 

chloride 4 d F,U 7.73 11.7 51.62 135.8 136.2 146.5 Thurston and Meyn 1984

Water flea,

Ceriodaphnia acanthina

Ammonium 

chloride 2 d F,M 7.06 24 104.8 154.3 154.3 Mount 1982

Water flea (<24 hr),

Ceriodaphnia dubia

Ammonium 

chloride 2 d S,M 8.02 24.8 21.26 141.1 Andersen and Buckley 1998

Water flea (<24 hr),

Ceriodaphnia dubia

Ammonium 

chloride 2 d S,M 7.5 25 47.05 129.2 Bailey et al. 2001

Water flea (<24 hr),

Ceriodaphnia dubia

Ammonium 

chloride 2 d S,M 7.5 25 56.84 156.1 Bailey et al. 2001

Water flea (<24 hr),

Ceriodaphnia dubia

Ammonium 

chloride 2 d S,M 8.16 22 24.77 170.5 Black 2001

Water flea (<24 hr),

Ceriodaphnia dubia

Ammonium 

chloride 2 d S,M 8.4 23 28.06 334.5 Black 2001

Water flea (<24 hr),

Ceriodaphnia dubia

Ammonium 

chloride 2 d S,M 8.4 23 32.63 389.0 Black 2001

Water flea (<24 hr),

Ceriodaphnia dubia

Ammonium 

chloride 2 d S,M 8 25 14.52 94.35 Scheller 1997

Water flea,

Ceriodaphnia dubia

Ammonium 

chloride 2 d S,M 8.08 24.75 15.6 114.5 Andersen and Buckley 1998

Water flea,

Ceriodaphnia dubia

Ammonium 

hydroxide 2 d R,M 8.4 26.4 7.412 117.1 Cowgill and Milazzo 1991
99

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Water flea,

Ceriodaphnia dubia

Ammonium 

sulfate 2 d R,NR 7.4 23 48.59 97.89 Manning et al. 1996

Water flea,

Ceriodaphnia dubia

Ammonium 

chloride 2 d R,M 7.8 25 33.98 152.9 Nimmo et al. 1989

Water flea,

Ceriodaphnia dubia

Ammonium 

chloride 2 d R,M 8.2 7 16.65 35.72 Nimmo et al. 1989

Water flea,

Ceriodaphnia dubia

Ammonium 

chloride 2 d S,M 7.85 23 28.65 119.5 Sarda 1994

Water flea,

Ceriodaphnia dubia

Ammonium 

chloride 2 d S,M 7.85 23 28.77 120.0 134.2 143.9 Sarda 1994

Water flea (adult),

Simocephalus vetulus

Ammonium 

chloride 2 d F,M 8.3 17 31.58 188.5 West 1985; Arthur et al. 1987

Water flea (adult),

Simocephalus vetulus

Ammonium 

chloride 2 d F,M 8.1 20.4 21.36 114.7 Arthur et al. 1987

Water flea,

Simocephalus vetulus

Ammonium 

chloride 2 d F,M 7.25 24.5 83.51 157.0 Mount 1982

Water flea,

Simocephalus vetulus

Ammonium 

chloride 2 d F,M 7.06 24 83.51 122.9 142.9 142.9 Mount 1982

Channel catfish,

Ictalurus punctatus

Ammonium 

chloride 4 d S,U 8.7 22 10.56 172.9 Colt and Tchobanoglous 1976

Channel catfish,

Ictalurus punctatus

Ammonium 

chloride 4 d S,U 8.7 26 10.19 166.9 Colt and Tchobanoglous 1976

Channel catfish,

Ictalurus punctatus

Ammonium 

chloride 4 d S,U 8.7 30 10.88 178.1 Colt and Tchobanoglous 1976

Channel catfish,

Ictalurus punctatus

Ammonium 

chloride 4 d S,M 7.49 19.7 131.5 235.0 EA Engineering 1985

Channel catfish,

Ictalurus punctatus

Ammonium 

chloride 4 d S,M 7.53 19.75 99.67 189.3 EA Engineering 1985

Channel catfish (larvae, 1 d),

Ictalurus punctatus

Ammonium 

chloride 4 d R,M 8.2 23.8 13.03 82.10 Bader and Grizzle 1992

Channel catfish (juvenile, 7 d),

Ictalurus punctatus

Ammonium 

chloride 4 d R,M 8.2 23.9 17.22 108.5 Bader and Grizzle 1992

Channel catfish (3.5 g),

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 7.8 19.6 44.71 132.9 West 1985; Arthur et al. 1987
100

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Channel catfish (5.8 g),

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 8 3.5 37.64 161.6 West 1985; Arthur et al. 1987

Channel catfish (6.4 g),

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 8.1 14.6 24.94 129.5 West 1985; Arthur et al. 1987

Channel catfish,

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 8.4 28 10.71 99.59 Colt and Tchobanoglous 1978

Channel catfish (3-11 mo),

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 7.46 10 124.8 213.5 DeGraeve et al. 1987

Channel catfish (3-11 mo),

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 7.41 15 113.1 180.2 DeGraeve et al. 1987

Channel catfish (3-11 mo),

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 7.41 20 89.63 142.8 DeGraeve et al. 1987

Channel catfish (3-11 mo),

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 7.45 20 72.15 121.7 DeGraeve et al. 1987

Channel catfish (3-11 mo),

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 7.4 25 89.41 140.5 DeGraeve et al. 1987

Channel catfish (3-11 mo),

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 7.41 25 85.69 136.5 DeGraeve et al. 1987

Channel catfish (3-11 mo),

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 7.44 30 65.25 108.5 DeGraeve et al. 1987

Channel catfish (<110 d),

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 8 20 15.09 64.77 Diamond et al. 1993

Channel catfish,

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 7.94 23.8 33.1 127.0 Reinbold and Pescitelli 1982d

Channel catfish,

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 7.98 23.8 30.49 126.1 Reinbold and Pescitelli 1982d

Channel catfish (4.5-10.8 g),

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 8.08 28 44.44 222.2 Roseboom and Richey 1977

Channel catfish (7.1-12.7 g),

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 8.09 22 32.33 164.8 Roseboom and Richey 1977

Channel catfish

(14.3 mm, 19.0 g),

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 7.93 20 74.35 277.4 Sparks 1975

Channel catfish (0.5 g),

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 7.8 25.7 32.85 97.67 Swigert and Spacie 1983
101

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Channel catfish,

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 8 26 32.34 138.8 West 1985

Channel catfish,

Ictalurus punctatus

Ammonium 

chloride 4 d F,M 8.1 17 40.83 212.1 142.4 142.4 West 1985

Red swamp crayfish (2.1 cm),

Procambarus clarkii

Ammonium 

chloride 4 d F,M 8 20 26.08 112.0 Diamond et al. 1993

Red swamp crayfish (<2.5 cm),

Procambarus clarkii

Ammonium 

chloride 4 d F,M 8 12 76.92 170.1 138.0 138.0 Diamond et al. 1993

Atlantic salmon (4.8-9.2 cm),

Salmo salar

Ammonium 

sulfate 4 d S,M 6.4 1.8 123 87.86 Knoph 1992

Atlantic salmon (4.8-9.2 cm),

Salmo salar

Ammonium 

sulfate 4 d S,M 6.4 1.8 133.9 95.64 Knoph 1992

Atlantic salmon (4.8-9.2 cm),

Salmo salar

Ammonium 

sulfate 4 d S,M 6 2.1 297.2 195.1 Knoph 1992

Atlantic salmon (4.8-9.2 cm),

Salmo salar

Ammonium 

sulfate 4 d S,M 6 2.1 341.1 223.9 Knoph 1992

Atlantic salmon (4.8-9.2 cm),

Salmo salar

Ammonium 

sulfate 4 d S,M 6.05 2.5 400 264.4 Knoph 1992

Atlantic salmon (4.8-9.2 cm),

Salmo salar

Ammonium 

sulfate 4 d S,M 6.05 2.5 491.7 325.0 Knoph 1992

Atlantic salmon (4.8-9.2 cm),

Salmo salar

Ammonium 

sulfate 4 d S,M 6 7.3 581.5 381.7 Knoph 1992

Atlantic salmon (4.8-9.2 cm),

Salmo salar

Ammonium 

sulfate 4 d S,M 6 7.3 587.6 385.7 Knoph 1992

Atlantic salmon (4.8-9.2 cm),

Salmo salar

Ammonium 

sulfate 4 d S,M 6.45 7.4 171.3 124.4 Knoph 1992

Atlantic salmon (4.8-9.2 cm),

Salmo salar

Ammonium 

sulfate 4 d S,M 6.45 7.4 214.4 155.7 Knoph 1992

Atlantic salmon (4.8-9.2 cm),

Salmo salar

Ammonium 

sulfate 4 d S,M 6.45 12.5 230.6 167.4 Knoph 1992

Atlantic salmon (4.8-9.2 cm),

Salmo salar

Ammonium 

sulfate 4 d S,M 6.45 12.5 248.3 180.3 Knoph 1992

Atlantic salmon (4.8-9.2 cm),

Salmo salar

Ammonium 

sulfate 4 d S,M 6.05 12.5 403.5 266.7 Knoph 1992
102

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Atlantic salmon (4.8-9.2 cm),

Salmo salar

Ammonium 

sulfate 4 d S,M 6.05 12.5 451.5 298.5 Knoph 1992

Atlantic salmon (4.8-9.2 cm),

Salmo salar

Ammonium 

sulfate 4 d S,M 6.05 17.1 356.1 235.4 Knoph 1992

Atlantic salmon (4.8-9.2 cm),

Salmo salar

Ammonium 

sulfate 4 d S,M 6.05 17.1 373 246.6 Knoph 1992

Atlantic salmon (1.5 g),

Salmo salar

Ammonium 

chloride 4 d S,M 7.45 8.5 60.29 101.7 Soderberg and Meade 1992

Atlantic salmon (1.5 g),

Salmo salar

Ammonium 

chloride 4 d S,M 7.45 8.5 35.74 60.26 Soderberg and Meade 1992

Atlantic salmon (36 g),

Salmo salar

Ammonium 

chloride 4 d S,M 7.45 8.5 118.2 199.3 Soderberg and Meade 1992

Atlantic salmon (36 g),

Salmo salar

Ammonium 

chloride 4 d S,M 7.45 8.5 70.62 119.1 183.3 Soderberg and Meade 1992

Brown trout (1.20 g, 5.4 cm),

Salmo trutta

Ammonium 

chloride 4 d F,U 7.85 13.2 29.58 96.20 Thurston and Meyn 1984

Brown trout (1.17 g, 5.3 cm),

Salmo trutta

Ammonium 

chloride 4 d. F,U 7.86 13.8 32.46 107.5 Thurston and Meyn 1984

Brown trout (0.91 g, 4.9 cm),

Salmo trutta

Ammonium 

chloride 4 d F,U 7.82 14.2 33.3 102.6 102.0 136.7 Thurston and Meyn 1984

White perch (76 mm),

Morone americana

Ammonium 

chloride 4 d S,M 8 16 14.93 64.09 Stevenson 1977

White perch (76 mm),

Morone americana

Ammonium 

chloride 4 d S,M 6 16 418.4 274.7 132.7 Stevenson 1977

White bass (4.4 g),

Morone chrysops

Ammonium 

chloride 4 d S,M 7.09 19.7 132.4 144.0 144.0 Ashe et al. 1996

Striped bass (20-93 mm),

Morone saxatilis

Ammonium 

chloride 4 d S,M 7.4 23.3 92.17 144.8 Hazel et al. 1971

Striped bass (20-93 mm),

Morone saxatilis

Ammonium 

chloride 4 d S,M 7.5 23.3 73.45 133.3 Hazel et al. 1971

Striped bass (20-93 mm),

Morone saxatilis

Ammonium 

chloride 4 d S,M 7.35 15 259.7 378.9 Hazel et al. 1971
103

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Striped bass (20-93 mm),

Morone saxatilis

Ammonium 

chloride 4 d S,M 7.5 15 182.3 330.7 Hazel et al. 1971

Striped bass (20-93 mm),

Morone saxatilis

Ammonium 

chloride 4 d S,M 7.93 23.3 48.03 180.8 Hazel et al. 1971

Striped bass (20-93 mm),

Morone saxatilis

Ammonium 

chloride 4 d S,M 7.5 23.3 125.9 228.5 Hazel et al. 1971

Striped bass (20-93 mm),

Morone saxatilis

Ammonium 

chloride 4 d S,M 7.84 15 165.7 524.6 Hazel et al. 1971

Striped bass (20-93 mm),

Morone saxatilis

Ammonium 

chloride 4 d S,M 7.5 15 354.9 644.0 Hazel et al. 1971

Striped bass (126.6 g),

Morone saxatilis

Ammonium 

chloride 4 d S,M 8.3 21 12.86 98.43 246.2 Oppenborn and Goudie 1993

Sunshine bass (larvae, 12 h),

Morone saxatilis x chrysops

Ammonium 

chloride 4 d S,M 8.5 18.7 3.903 43.99 Harcke and Daniels 1999

Sunshine bass (367.2 g),

Morone saxatilis x chrysops

Ammonium 

chloride 4 d S,M 8.3 21 8.147 62.37 Oppenborn and Goudie 1993

Sunshine bass (42.7 g),

Morone saxatilis x chrysops

Ammonium 

chloride 4 d S,M 7 25 63.62 63.62 Weirich et al. 1993

Sunshine bass (42.7 g),

Morone saxatilis x chrysops

Ammonium 

chloride 4 d S,M 7 25 83.06 83.06 Weirich et al. 1993

Sunshine bass (42.7 g),

Morone saxatilis x chrysops

Ammonium 

chloride 4 d S,M 7 25 56.55 56.55 Weirich et al. 1993

Sunshine bass (42.7 g),

Morone saxatilis x chrysops

Ammonium 

chloride 4 d S,M 7 25 65.39 65.39 Weirich et al. 1993

Sunshine bass (42.7 g),

Morone saxatilis x chrysops

Ammonium 

chloride 4 d S,M 7 25 60.09 60.09 Weirich et al. 1993

Sunshine bass (42.7 g),

Morone saxatilis x chrysops

Ammonium 

chloride 4 d S,M 7 25 64.51 64.51 Weirich et al. 1993

Sunshine bass (42.7 g),

Morone saxatilis x chrysops

Ammonium 

chloride 4 d S,M 7 25 79.53 79.53 Weirich et al. 1993

Sunshine bass (42.7 g),

Morone saxatilis x chrysops

Ammonium 

chloride 4 d S,M 7 25 86.6 86.60 Weirich et al. 1993

Sunshine bass (42.7 g),

Morone saxatilis x chrysops

Ammonium 

chloride 4 d S,M 7 25 95.43 95.43 Weirich et al. 1993
104

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Sunshine bass (42.7 g),

Morone saxatilis x chrysops

Ammonium 

chloride 4 d S,M 7 25 105.2 105.2 70.22 134.8 Weirich et al. 1993

Water flea,

Daphnia magna

Ammonium 

chloride 2 d S,M 8.5 20 26.34 296.9 Gersich and Hopkins 1986

Water flea,

Daphnia magna

Ammonium 

chloride 2 d S,M 7.92 21 9.463 37.66 Gulyas and Fleit 1990

Water flea,

Daphnia magna

Ammonium 

chloride 2 d S,M 8.2 25 20.71 197.5 Parkhurst et al. 1979, 1981

Water flea,

Daphnia magna

Ammonium 

chloride 2 d R,U 8.34 19.7 51.92 419.1 Reinbold and Pescitelli 1982a

Water flea,

Daphnia magna

Ammonium 

chloride 2 d S,M 8.07 19.6 51.09 242.4 Russo et al. 1985

Water flea,

Daphnia magna

Ammonium 

chloride 2 d S,M 7.51 20.1 48.32 89.74 Russo et al. 1985

Water flea,

Daphnia magna

Ammonium 

chloride 2 d S,M 7.53 20.1 55.41 106.1 Russo et al. 1985

Water flea,

Daphnia magna

Ammonium 

chloride 2 d S,M 7.5 20.3 43.52 80.98 Russo et al. 1985

Water flea,

Daphnia magna

Ammonium 

chloride 2 d S,M 7.4 20.6 42.31 69.88 Russo et al. 1985

Water flea,

Daphnia magna

Ammonium 

chloride 2 d S,M 8.09 20.9 41.51 227.9 Russo et al. 1985

Water flea,

Daphnia magna

Ammonium 

chloride 2 d S,M 7.95 22 51.3 236.7 Russo et al. 1985

Water flea,

Daphnia magna

Ammonium 

chloride 2 d S,M 8.15 22 37.44 252.8 Russo et al. 1985

Water flea,

Daphnia magna

Ammonium 

chloride 2 d S,M 8.04 22.8 38.7 226.1 157.7 Russo et al. 1985

Water flea,

Daphnia pulicaria

Ammonium 

chloride 2 d F,M 8.05 14 34.5 99.03 99.03 125.0 DeGraeve et al. 1980

Clawed toad (embryo),

Xenopus laevis

Ammonium 

sulfate 4 d R,M 7.2 22 38.59 40.91 Schuytema and Nebeker 1999a
105

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Clawed toad (embryo),

Xenopus laevis

Ammonium 

sulfate 4 d R,M 7.2 22 119.6 126.8 Schuytema and Nebeker 1999a

Clawed toad (embryo),

Xenopus laevis

Ammonium 

nitrate 4 d R,M 7.2 24 32.37 39.55 Schuytema and Nebeker 1999a

Clawed toad (embryo),

Xenopus laevis

Ammonium 

sulfate 4 d R,M 7.2 24 60.71 74.17 Schuytema and Nebeker 1999a

Clawed toad

(17 mg, Gosner Stage 26-27),

Xenopus laevis

Nitric acid

ammonium salt 4 d R,M 7.15 22 101.4 117.2 Schuytema and Nebeker 1999b

Clawed toad

(17 mg, Gosner Stage 26-27),

Xenopus laevis

Ammonium 

sulfate 4 d R,M 7.15 22 135.9 157.2 Schuytema and Nebeker 1999b

Clawed toad

(21 mg, Gosner Stage 26-27),

Xenopus laevis

Ammonium 

chloride 4 d R,M 7.15 22 128.3 148.4 Schuytema and Nebeker 1999b

Clawed toad (embryo),

Xenopus laevis

Ammonium 

phosphate 4 d R,M 8.43 25 37.3 367.4 Tietge et al. 2000

Clawed toad (embryo),

Xenopus laevis

Ammonium 

phosphate 4 d R,M 8.62 25 28.7 405.6 122.5 122.5 Tietge et al. 2000

Flatworm,

Dendrocoelum lacteum

Ammonium 

chloride 4 d S,U 8.2 18 22.37 119.5 119.5 119.5 Stammer 1953

Walleye,

Sander vitreus

Ammonium 

chloride 4 d F,U 8.08 18.2 17.43 87.13 Reinbold and Pescitelli 1982a

Walleye (22.6 g),

Sander vitreus

Ammonium 

chloride 4 d F,M 7.9 3.7 48.37 172.3 West 1985; Arthur et al. 1987

Walleye (19.4 g),

Sander vitreus

Ammonium 

chloride 4 d F,M 7.7 11.1 89.93 224.8 West 1985; Arthur et al. 1987

Walleye (13.4 g),

Sander vitreus

Ammonium 

chloride 4 d F,M 8.3 19 6.123 46.87 West 1985; Arthur et al. 1987

Walleye (3.0 g, 65.6 mm),

Sander vitreus

Ammonium 

chloride 4 d F,M 8.06 21.5 21.49 103.4 117.1 117.1 Mayes et al. 1986

Central stoneroller (2.1 g),

Campostoma anomalum

Ammonium 

chloride 4 d F,M 7.8 25.7 38.97 115.9 115.9 115.9 Swigert and Spacie 1983
106

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Rainbow dace,

Cyprinella lutrensis

Ammonium 

chloride 4 d F,M 8.3 24 24.37 186.5 Hazel et al. 1979

Rainbow dace,

Cyprinella lutrensis

Ammonium 

chloride 4 d F,M 9.1 24 6.502 206.1 196.1 Hazel et al. 1979

Spotfin shiner (31-85 mm),

Cyprinella spiloptera

Ammonium

chloride 4 d F,M 7.95 26.5 18.52 72.39 Rosage et al. 1979

Spotfin shiner (41-78 mm),

Cyprinella spiloptera

Ammonium 

chloride 4 d F,M 8.15 26.5 16.27 93.07 Rosage et al. 1979

Spotfin shiner (0.5 g),

Cyprinella spiloptera

Ammonium 

chloride 4 d F,M 7.9 25.7 24.52 87.36 83.80 Swigert and Spacie 1983

Steelcolor shiner (0.5 g),

Cyprinella whipplei

Ammonium 

chloride 4 d F,M 7.9 25.7 22.72 80.94 80.94 110.0 Swigert and Spacie 1983

Dwarf wedgemussel 

(glochidia),

Alasmidonta heterodon

Ammonium 

chloride 1 d S,M 8.3 20 >14.24 c

>109.0 >109.0 >109.0 Wang et al. 2007b

Pink papershell (glochidia),

Potamilus ohiensis

Ammonium 

chloride 1 d S,M 8.3 20 >14.24 c

>109.0 >109.0 >109.0 Wang et al. 2007b

Green sunfish

(larvae, 9 d swim up fry),

Lepomis cyanellus

Ammonium 

chloride 4 d F,U 8.28 26.2 8.43 62.07 Reinbold and Pescitelli 1982a

Green sunfish,

Lepomis cyanellus

Ammonium 

chloride 4 d F,M 7.84 12.3 33.09 105.7 Jude 1973

Green sunfish (62.5 mg),

Lepomis cyanellus

Ammonium 

chloride 4 d F,M 7.2 22.4 142.9 174.5 McCormick et al. 1984

Green sunfish (62.5 mg),

Lepomis cyanellus

Ammonium 

chloride 4 d F,M 6.61 22.4 254.5 197.0 McCormick et al. 1984

Green sunfish (62.5 mg),

Lepomis cyanellus

Ammonium 

chloride 4 d F,M 7.72 22.4 55.79 144.3 McCormick et al. 1984

Green sunfish (62.5 mg),

Lepomis cyanellus

Ammonium 

chloride 4 d F,M 8.69 22.4 9.24 148.6 150.8 McCormick et al. 1984
107

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Pumpkinseed (4.13-9.22 g),

Lepomis gibbosus

Ammonium 

chloride 4 d F,M 7.77 12 9.11 25.69 Jude 1973

Pumpkinseed,

Lepomis gibbosus

Ammonium 

chloride 4 d F,M 7.77 14 48.09 135.6 Thurston 1981

Pumpkinseed,

Lepomis gibbosus

Ammonium 

chloride 4 d F,M 7.77 14.5 42.02 118.5 Thurston 1981

Pumpkinseed,

Lepomis gibbosus

Ammonium 

chloride 4 d F,M 7.71 15.7 48.54 87.54 77.53 Thurston 1981

Bluegill,

Lepomis macrochirus

Ammonium 

chloride 4 d S,M 7.51 20.35 40.41 73.88 EA Engineering 1985

Bluegill,

Lepomis macrochirus

Ammonium 

chloride 4 d S,M 7.51 20.35 41.96 76.72 EA Engineering 1985

Bluegill,

Lepomis macrochirus

Ammonium 

chloride 4 d S,M 7.52 20.65 41.9 78.36 EA Engineering 1985

Bluegill,

Lepomis macrochirus

Ammonium 

chloride 4 d S,M 7.51 20.35 44.3 80.98 EA Engineering 1985

Bluegill,

Lepomis macrochirus

Ammonium 

chloride 4 d S,M 7.52 20.65 42.63 79.73 EA Engineering 1985

Bluegill,

Lepomis macrochirus

Ammonium 

chloride 4 d S,M 7.52 20.65 44.1 82.48 EA Engineering 1985

Bluegill (1.7 cm),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 8 20 21.56 92.54 Diamond et al. 1993

Bluegill,

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 8 12 25.12 107.9 Diamond et al. 1993

Bluegill

(20.0-70.0 mm, young of year),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 8.11 18.5 16.73 88.57 Emery and Welch 1969

Bluegill

(20.0-70.0 mm, young of year),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 8.24 18.5 42.01 286.1 Emery and Welch 1969

Bluegill

(20.0-70.0 mm, young of year),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 8.75 18.5 12.7 227.4 Emery and Welch 1969
108

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Bluegill

(20.0-70.0 mm, young of year),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 9.05 18.5 6.581 193.8 Emery and Welch 1969

Bluegill

(20.0-70.0 mm, young of year),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 9.19 18.5 3.755 135.0 Emery and Welch 1969

Bluegill

(20.0-70.0 mm, young of year),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 9.62 18.5 0.7859 44.84 Emery and Welch 1969

Bluegill

(20.0-70.0 mm, young of year),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 9.85 18.5 1.346 89.70 Emery and Welch 1969

Bluegill,

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 8.6 24 5.509 75.01 Hazel et al. 1979

Bluegill (5.2 cm),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 7.9 24.25 33.06 117.8 Lubinski et al. 1974

Bluegill (0.38 g, 26.3 mm),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 8.1 22 19.39 100.7 Mayes et al. 1986

Bluegill (19 mm, 0.0781 g),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 8.4 4 14.64 136.1 Reinbold and Pescitelli 1982b

Bluegill (22 mm, 0.1106 g),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 8.12 25 23.37 126.2 Reinbold and Pescitelli 1982b

Bluegill (28 mm, 0.250 g),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 8.16 4.5 12.55 73.19 Reinbold and Pescitelli 1982b

Bluegill (30 mm, 0.267 g),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 8.09 24.8 17.22 87.75 Reinbold and Pescitelli 1982b

Bluegill (217 mg),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 8 22 12.75 54.74 Roseboom and Richey 1977

Bluegill (342 mg),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 8.2 28 14.81 93.31 Roseboom and Richey 1977

Bluegill (646 mg),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 7.93 22 24.08 90.66 Roseboom and Richey 1977

Bluegill (72 mg),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 8.07 22 8.846 43.38 Roseboom and Richey 1977

Bluegill,

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 7.6 21.7 44.03 93.31 Smith et al. 1984
109

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Bluegill (4.8 cm, 1.1 g),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 7.85 22.05 59.93 194.9 Sparks 1975

Bluegill (0.9 g),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 7.8 24.2 33.88 100.7 Swigert and Spacie 1983

Bluegill (0.9 g),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 7.6 26.5 58.69 124.4 Swigert and Spacie 1983

Bluegill (1.2 g),

Lepomis macrochirus

Ammonium 

chloride 4 d F,M 7.8 26.6 37.52 111.6 104.5 106.9 Swigert and Spacie 1983

Common carp (206 mg),

Cyprinus carpio

Ammonium 

chloride 4 d R,M 7.72 28 51.78 133.9 Hasan and MacIntosh 1986

Common carp (299 mg),

Cyprinus carpio

Ammonium 

chloride 4 d R,M 7.72 28 48.97 126.6 Hasan and MacIntosh 1986

Common carp (4-5 cm),

Cyprinus carpio

Ammonium 

chloride 4 d R,M 7.4 28 45.05 70.78 106.3 106.3 Rao et al. 1975

Golden trout (0.09 g, 24 cm),

Oncorhynchus aguabonita

Ammonium 

chloride 4 d F,M 8.06 13.2 23.3 112.1 112.1 Thurston and Russo 1981

Cutthroat trout (3.6 g),

Oncorhynchus clarkii

Ammonium 

chloride 4 d F,M 7.7 10 17.3 43.24 Thurston et al. 1981a

Cutthroat trout (3.6 g),

Oncorhynchus clarkii

Ammonium 

chloride 4 d F,M 7.7 10 29.1 72.73 Thurston et al. 1981a

Cutthroat trout (4.1 g),

Oncorhynchus clarkii

Ammonium 

chloride 4 d F,M 7.7 10 19.3 48.24 Thurston et al. 1981a

Cutthroat trout (4.1 g),

Oncorhynchus clarkii

Ammonium 

chloride 4 d F,M 7.7 10 26.3 65.73 Thurston et al. 1981a

Cutthroat trout (3.4 g),

Oncorhynchus clarkii

Ammonium 

chloride 4 d F,M 7.78 12.2 32.57 93.49 Thurston et al. 1978

Cutthroat trout (3.3 g),

Oncorhynchus clarkii

Ammonium 

chloride 4 d F,M 7.8 12.4 36.55 108.7 Thurston et al. 1978

Cutthroat trout (1.0 g),

Oncorhynchus clarkii

Ammonium 

chloride 4 d F,M 7.8 12.8 37.75 112.2 Thurston et al. 1978

Cutthroat trout (1.0 g),

Oncorhynchus clarkii

Ammonium 

chloride 4 d F,M 7.81 13.1 43.72 132.3 78.92 Thurston et al. 1978
110

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Pink salmon (late alevins),

Oncorhynchus gorbuscha

Ammonium 

sulfate 4 d S,M 6.4 4.3 230.5 164.6 Rice and Bailey 1980

Pink salmon (fry),

Oncorhynchus gorbuscha

Ammonium 

sulfate 4 d S,M 6.4 4.3 277.7 198.3 180.7 Rice and Bailey 1980

Coho salmon (6 g),

Oncorhynchus kisutch

Ammonium 

chloride 4 d F,M 8.1 17.2 11.59 60.20 Buckley 1978

Coho salmon,

Oncorhynchus kisutch

Ammonium 

chloride 4 d F,M 7 15 82.02 82.02 Wilson 1974; RobinsonWilson and Seim 1975

Coho salmon,

Oncorhynchus kisutch

Ammonium 

chloride 4 d F,M 7 15 84.43 84.43 Wilson 1974; RobinsonWilson and Seim 1975

Coho salmon,

Oncorhynchus kisutch

Ammonium 

chloride 4 d F,M 7.5 15 50.65 91.90 Wilson 1974; RobinsonWilson and Seim 1975

Coho salmon,

Oncorhynchus kisutch

Ammonium 

chloride 4 d F,M 7.5 15 52.76 95.73 Wilson 1974; RobinsonWilson and Seim 1975

Coho salmon,

Oncorhynchus kisutch

Ammonium 

chloride 4 d F,M 8 15 21.63 92.84 Wilson 1974; RobinsonWilson and Seim 1975

Coho salmon,

Oncorhynchus kisutch

Ammonium 

chloride 4 d F,M 8 15 22 94.44 Wilson 1974; RobinsonWilson and Seim 1975

Coho salmon,

Oncorhynchus kisutch

Ammonium 

chloride 4 d F,M 8.5 15 9.093 102.5 87.05 Wilson 1974; RobinsonWilson and Seim 1975

Rainbow trout (0.5-3.0 g),

Oncorhynchus mykiss

Ammonium 

sulfate 4 d S,U 7.95 15 51.06 199.6 Qureshi et al. 1982

Rainbow trout

(McConaughy strain, 251 mg),

Oncorhynchus mykiss

Ammonium 

chloride 4 d S,M 6.84 12 112 98.86 Buhl and Hamilton 2000

Rainbow trout,

Oncorhynchus mykiss

Ammonium 

chloride 4 d S,M 7.55 15 34.23 67.04 Craig and Beggs 1979

Rainbow trout (0.80 g),

Oncorhynchus mykiss - 4 d S,M 6.95 14.7 163.6 156.9 Environment Canada 2004

Rainbow trout (0.60 g),

Oncorhynchus mykiss - 4 d S,M 6.97 14.5 144 140.3 Environment Canada 2004

Rainbow trout (0.63 g),

Oncorhynchus mykiss - 4 d S,M 7.02 15.4 146.7 149.4 Environment Canada 2004
111

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Rainbow trout (0.80 g),

Oncorhynchus mykiss - 4 d S,M 7.02 14.6 159 161.8 Environment Canada 2004

Rainbow trout (0.80 g),

Oncorhynchus mykiss - 4 d S,M 7.03 15.1 156.6 160.9 Environment Canada 2004

Rainbow trout (0.90 g),

Oncorhynchus mykiss - 4 d S,M 7.18 15.1 141.6 169.2 Environment Canada 2004

Rainbow trout (2.01 g),

Oncorhynchus mykiss - 4 d S,M 7.45 15.1 104.4 176.0 Environment Canada 2004

Rainbow trout (1.30 g),

Oncorhynchus mykiss - 4 d S,M 7.47 14.7 72.65 126.1 Environment Canada 2004

Rainbow trout (0.78 g),

Oncorhynchus mykiss - 4 d S,M 7.47 14.5 79.67 138.3 Environment Canada 2004

Rainbow trout (0.40 g),

Oncorhynchus mykiss - 4 d S,M 7.51 14.2 73.71 135.8 Environment Canada 2004

Rainbow trout (1.64 g),

Oncorhynchus mykiss - 4 d S,M 7.54 14.6 75.3 145.2 Environment Canada 2004

Rainbow trout (1.13 g),

Oncorhynchus mykiss - 4 d S,M 7.59 13.9 59.4 123.9 Environment Canada 2004

Rainbow trout (1.50 g),

Oncorhynchus mykiss - 4 d S,M 7.87 15.1 42.9 144.7 Environment Canada 2004

Rainbow trout (1.38 g),

Oncorhynchus mykiss - 4 d S,M 7.93 15.2 41.15 155.0 Environment Canada 2004

Rainbow trout (0.90 g),

Oncorhynchus mykiss - 4 d S,M 7.97 15.2 36.17 145.4 Environment Canada 2004

Rainbow trout (1.00 g),

Oncorhynchus mykiss - 4 d S,M 7.98 15.1 35.29 145.9 Environment Canada 2004

Rainbow trout (1.30 g),

Oncorhynchus mykiss - 4 d S,M 8.03 14.9 23.03 104.6 Environment Canada 2004

Rainbow trout (1.26 g),

Oncorhynchus mykiss - 4 d S,M 8.04 14.3 25.84 119.7 Environment Canada 2004

Rainbow trout (1.60 g),

Oncorhynchus mykiss - 4 d S,M 8.34 15.3 19.15 158.5 Environment Canada 2004

Rainbow trout (1.30 g),

Oncorhynchus mykiss - 4 d S,M 8.39 15.3 12.05 109.9 Environment Canada 2004

Rainbow trout (1.11 g),

Oncorhynchus mykiss - 4 d S,M 8.4 14.9 12.84 119.4 Environment Canada 2004
112

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Rainbow trout (1.40 g),

Oncorhynchus mykiss - 4 d S,M 8.44 14.7 14.41 144.7 Environment Canada 2004

Rainbow trout (0.90 g),

Oncorhynchus mykiss - 4 d S,M 8.46 14.5 11.82 123.4 Environment Canada 2004

Rainbow trout (1.26 g),

Oncorhynchus mykiss - 4 d S,M 8.47 14.3 17.2 183.0 Environment Canada 2004

Rainbow trout (1.01 g),

Oncorhynchus mykiss - 4 d S,M 8.93 14.2 4.8 117.0 Environment Canada 2004

Rainbow trout (1.44 g),

Oncorhynchus mykiss - 4 d S,M 8.93 15 5.4 131.6 Environment Canada 2004

Rainbow trout (1.42 g),

Oncorhynchus mykiss - 4 d S,M 9.46 14.6 1.6 79.03 Environment Canada 2004

Rainbow trout,

Oncorhynchus mykiss - 4 d S,M 7.5 15 38.37 69.63 Holt and Malcolm 1979

Rainbow trout (129 mm),

Oncorhynchus mykiss

Phosphoric acid,

Diammonium 

salt

4 d F,U 7 15 207.5 207.5 Blahm 1978

Rainbow trout (1.7-1.9 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,U 7.4 14.5 20.03 31.47 Calamari et al. 1981

Rainbow trout,

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,U 7.4 14.5 46.31 72.77 Calamari et al. 1981

Rainbow trout (8-10 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,U 7.4 14.5 55.07 86.53 Calamari et al. 1981

Rainbow trout (129 mm),

Oncorhynchus mykiss

Phosphoric acid,

Diammonium 

salt

4 d F,U 8 15 70 300.5 Blahm 1978

Rainbow trout (10.9 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.7 3.6 38.52 96.27 West 1985; Arthur et al. 1987

Rainbow trout (14.0 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.7 9.8 55.15 137.8 West 1985; Arthur et al. 1987

Rainbow trout (22.4 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.9 16.2 15.23 54.24 West 1985; Arthur et al. 1987

Rainbow trout (10.3 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.9 11.3 30.15 107.4 West 1985; Arthur et al. 1987

Rainbow trout (3.3 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 8.3 18.7 12.75 97.57 West 1985; Arthur et al. 1987
113

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Rainbow trout (53 mm, 1.48 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.95 10 35.14 137.3 Broderius and Smith Jr. 1979

Rainbow trout (stage 8),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.4 14.4 40.99 64.40 Calamari et al. 1977

Rainbow trout,

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 8.05 14 22.9 108.1 DeGraeve et al. 1980

Rainbow trout (45 mm, 0.86 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 8.16 14.2 23.39 136.4 Reinbold and Pescitelli 1982b

Rainbow trout

(119 mm, 20.6 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 8.28 12.8 15.4 113.4 Reinbold and Pescitelli 1982b

Rainbow trout

(115 mm, 18.1 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 8.34 5 17.32 143.3 Reinbold and Pescitelli 1982b

Rainbow trout (42 mm, 0.61 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 8.43 3 11.86 116.8 Reinbold and Pescitelli 1982b

Rainbow trout (52 mm, 1.47 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 8.5 14.9 10.09 113.7 Reinbold and Pescitelli 1982b

Rainbow trout (44 mm, 0.76 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 8.6 3.3 15.27 207.9 Reinbold and Pescitelli 1982b

Rainbow trout (6.3 g, 8.1 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.44 12.8 32.49 54.00 Thurston and Russo 1983

Rainbow trout (8.0 g, 8.9 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.5 14.5 24.2 43.91 Thurston and Russo 1983

Rainbow trout

(29.8 g, 13.1 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.59 12.7 32.62 68.03 Thurston and Russo 1983

Rainbow trout

(28.0 g, 13.1 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.6 13 23.8 50.43 Thurston and Russo 1983

Rainbow trout

(24.5 g, 12.7 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.6 12.9 25.14 53.27 Thurston and Russo 1983

Rainbow trout

(2596 g, 57.0 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.62 7.9 20.53 44.93f Thurston and Russo 1983
114

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Rainbow trout 

(15.1 g, 10.7 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.62 14.4 28.62 62.64 Thurston and Russo 1983

Rainbow trout

(29.6 g, 13.3 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.63 12.9 25.65 57.06 Thurston and Russo 1983

Rainbow trout

(1496 g, 48.5 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.64 9.8 25.82 58.38f Thurston and Russo 1983

Rainbow trout

(18.9 g, 11.6 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.64 13.1 29.28 66.21 Thurston and Russo 1983

Rainbow trout

(558 g, 37.0 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.64 10 31.85 72.02 Thurston and Russo 1983

Rainbow trout

(1698 g, 50.9 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.65 9.8 19.46 44.73f Thurston and Russo 1983

Rainbow trout

(22.8 g, 12.3 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.65 13.2 28.64 65.84 Thurston and Russo 1983

Rainbow trout

(12.3 g, 10.2 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.65 14.3 29.02 66.71 Thurston and Russo 1983

Rainbow trout

(513 g, 35.9 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.66 9.8 25.95 60.65 Thurston and Russo 1983

Rainbow trout

(22.6 g, 12.3 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.66 13.6 28.27 66.07 Thurston and Russo 1983

Rainbow trout

(26.0 g, 13.0 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.66 12.8 33.97 79.39 Thurston and Russo 1983

Rainbow trout

(14.8 g, 10.5 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.67 14 27.3 64.87 Thurston and Russo 1983
115

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Rainbow trout

(38.0 g, 14.4 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.68 13 33.15 80.11 Thurston and Russo 1983

Rainbow trout

(1122 g, 45.6 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.69 10.4 17.75 43.62f Thurston and Russo 1983

Rainbow trout

(1140 g, 46.4 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.69 10.7 20.18 49.59f Thurston and Russo 1983

Rainbow trout

(152 g, 23.4 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.69 10.7 25.62 62.96 Thurston and Russo 1983

Rainbow trout

(23.6 g, 13.2 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.69 13.4 27.51 67.60 Thurston and Russo 1983

Rainbow trout (9.5 g, 9.4 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.9 12.7 20.03 71.36 Thurston and Russo 1983

Rainbow trout (4.3 g, 7.1 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.71 11.5 30.22 76.83 Thurston and Russo 1983

Rainbow trout (4.0 g, 7.0 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.71 11.4 32.02 81.40 Thurston and Russo 1983

Rainbow trout

(248 g, 25.2 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.74 10.4 25.76 68.95 Thurston and Russo 1983

Rainbow trout

(25.8 g, 13.6 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.75 11.8 31.53 85.87 Thurston and Russo 1983

Rainbow trout (8.1 g, 9.3 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.75 12.3 33.94 92.43 Thurston and Russo 1983

Rainbow trout

(380 g, 32.4 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.76 10 22.44 62.19 Thurston and Russo 1983

Rainbow trout

(42.0 g, 16.0 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.77 13.6 31.81 89.71 Thurston and Russo 1983
116

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Rainbow trout (1.7 g, 5.7 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.79 12.4 41.97 122.6 Thurston and Russo 1983

Rainbow trout

(11.2 g, 10.0 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.8 9.7 23.65 70.32 Thurston and Russo 1983

Rainbow trout (5.7 g, 8.4 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.8 13.3 42.02 124.9 Thurston and Russo 1983

Rainbow trout (2.3 g, 6.1 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.8 12.4 47.87 142.3 Thurston and Russo 1983

Rainbow trout (8.0 g, 9.5 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.82 13.2 33.67 103.7 Thurston and Russo 1983

Rainbow trout (4.6 g, 7.4 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.83 13.5 33.55 105.2 Thurston and Russo 1983

Rainbow trout (6.7 g, 8.6 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.84 12.2 24.54 78.38 Thurston and Russo 1983

Rainbow trout (9.0 g, 9.3 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.84 12.9 32.3 103.2 Thurston and Russo 1983

Rainbow trout (1.8 g, 5.7 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.84 13.8 33.09 105.7 Thurston and Russo 1983

Rainbow trout (4.3 g, 7.1 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.84 13 38.69 123.6 Thurston and Russo 1983

Rainbow trout (0.47 g, 4.0 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.85 12.5 29.77 96.81 Thurston and Russo 1983

Rainbow trout (2.5 g, 6.0 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.85 13.1 31.55 102.6 Thurston and Russo 1983

Rainbow trout (0.61 g, 4.3 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.85 13.1 33.59 109.2 Thurston and Russo 1983

Rainbow trout (1.02 g, 4.9 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.85 12.3 33.99 110.5 Thurston and Russo 1983

Rainbow trout (9.4 g, 9.6 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.85 16.1 34.17 111.1 Thurston and Russo 1983

Rainbow trout (0.33 g, 3.6 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.86 13 20.7 68.55 Thurston and Russo 1983

Rainbow trout (0.33 g, 3.6 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.86 13.4 23.71 78.52 Thurston and Russo 1983
117

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Rainbow trout (0.47 g, 4.0 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.86 12.7 28.77 95.27 Thurston and Russo 1983

Rainbow trout (1.7 g, 5.8 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.86 14.1 34.95 115.7 Thurston and Russo 1983

Rainbow trout

(48.6 g, 15.2 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.86 10.2 35.31 116.9 Thurston and Russo 1983

Rainbow trout (0.15 g, 2.7 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.87 12.9 16.81 56.69 Thurston and Russo 1983

Rainbow trout (0.18 g, 2.9 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.87 12.9 18.99 64.04 Thurston and Russo 1983

Rainbow trout (0.23 g, 3.2 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.87 13.1 19.08 64.34 Thurston and Russo 1983

Rainbow trout (7.0 g, 8.8 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.87 12.2 20.02 67.51 Thurston and Russo 1983

Rainbow trout (0.18 g, 2.9 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.87 13 21.15 71.32 Thurston and Russo 1983

Rainbow trout (2.6 g, 6.2 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.87 12.1 31.8 107.2 Thurston and Russo 1983

Rainbow trout (11.1 g, 9.9 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.87 13 34.32 115.7 Thurston and Russo 1983

Rainbow trout (0.12 g, 2.4 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.88 12.8 11.07 38.02 Thurston and Russo 1983

Rainbow trout (0.14 g, 2.6 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.88 12.9 15.91 54.64 Thurston and Russo 1983

Rainbow trout (0.23 g, 3.2 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.88 13.4 19.43 66.73 Thurston and Russo 1983

Rainbow trout

(52.1 g, 15.5 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.88 10 28.6 98.22 Thurston and Russo 1983

Rainbow trout (1.8 g, 5.9 cm),

Oncorhynchus mykiss

Ammonium 

sulfate 4 d F,M 7.89 12.4 36.73 128.5 Thurston and Russo 1983

Rainbow trout (0.06 g, 1.7 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.9 13.4 19.44 69.26 Thurston and Russo 1983

Rainbow trout (0.06 g, 1.7 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.7 13.9 28.54 71.33 Thurston and Russo 1983
118

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Rainbow trout (7.9 g, 9.2 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.9 11.9 22.65 80.69 Thurston and Russo 1983

Rainbow trout (9.7 g, 9.7 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.9 13 35.75 127.4 Thurston and Russo 1983

Rainbow trout (9.3 g, 9.0 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.9 13 37.41 133.3 Thurston and Russo 1983

Rainbow trout (0.08 g, 2.0 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.91 13.1 12.68 46.01 Thurston and Russo 1983

Rainbow trout (0.06 g, 1.7 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.91 13 20.99 76.17 Thurston and Russo 1983

Rainbow trout (7.1 g, 8.4 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.91 19 25.36 92.03 Thurston and Russo 1983

Rainbow trout (10.1 g, 9.8 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.91 19.1 26.44 95.95 Thurston and Russo 1983

Rainbow trout (1.7 g, 5.8 cm),

Oncorhynchus mykiss

Phosphoric acid,

Diammonium 

salt

4 d F,M 7.94 12.8 26.49 101.6 Thurston and Russo 1983

Rainbow trout (2.1 g, 6.2 cm),

Oncorhynchus mykiss

Ammonium 

sulfate 4 d F,M 7.94 12.5 39.25 150.6 Thurston and Russo 1983

Rainbow trout (0.15 g, 2.7 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.95 12.5 19.75 77.19 Thurston and Russo 1983

Rainbow trout (8.6 g, 8.9 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.96 19.2 23.21 92.42 Thurston and Russo 1983

Rainbow trout (2.1 g, 6.2 cm),

Oncorhynchus mykiss

Phosphoric acid,

Diammonium 

salt

4 d F,M 7.98 12.5 27.02 111.7 Thurston and Russo 1983

Rainbow trout (1.01 g, 4.6 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 8.06 13.2 33.64 161.8 Thurston and Russo 1983

Rainbow trout (0.36 g, 3.4 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 8.08 12.8 23.05 115.2 Thurston and Russo 1983

Rainbow trout (1.7 g, 5.9 cm),

Oncorhynchus mykiss

Ammonium 

bicarbonate 4 d F,M 8.1 13.9 18.14 94.23 Thurston and Russo 1983

Rainbow trout (1.8 g, 5.8 cm),

Oncorhynchus mykiss

Ammonium 

bicarbonate 4 d F,M 8.12 13.6 17.34 93.61 Thurston and Russo 1983

Rainbow trout (2596 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.62 7.9 21.6 47.27 Thurston et al. 1981a
119

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Rainbow trout (2080 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.67 7.7 17 40.40 Thurston et al. 1981a

Rainbow trout (293 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.71 8.5 20.7 52.62 Thurston et al. 1981a

Rainbow trout (230 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.72 8.2 10.5 27.15 Thurston et al. 1981a

Rainbow trout (244 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.72 8.1 19.8 51.20 Thurston et al. 1981a

Rainbow trout (230 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.74 8.3 22.3 59.69 Thurston et al. 1981a

Rainbow trout (247 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.74 8.1 28 74.94 Thurston et al. 1981a

Rainbow trout (18 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.86 9.6 19.3 63.91 Thurston et al. 1981a

Rainbow trout (21 g),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.86 9.7 31.6 104.6 Thurston et al. 1981a

Rainbow trout (4.6 g, 7.3 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.75 12.7 32.09 87.39 Thurston et al. 1981b

Rainbow trout (5.7 g, 8.0 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.75 12.5 36.97 100.7 Thurston et al. 1981b

Rainbow trout (5.0 g, 7.6 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.76 12.5 39.08 108.3 Thurston et al. 1981b

Rainbow trout (5.7 g, 8.0 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.79 12.9 40.88 119.4 Thurston et al. 1981b

Rainbow trout (4.0 g, 7.2 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.83 12.8 36.49 114.5 Thurston et al. 1981b

Rainbow trout (9.5 g, 9.4 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 6.51 14.1 157.4 116.8 Thurston et al. 1981c

Rainbow trout (9.5 g, 9.4 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 6.8 14.1 94.05 80.83 Thurston et al. 1981c

Rainbow trout (9.5 g, 9.4 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.3 14 74.2 102.2 Thurston et al. 1981c

Rainbow trout (9.5 g, 9.4 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 8.29 14.1 13.85 104.0 Thurston et al. 1981c

Rainbow trout (9.5 g, 9.4 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 8.82 13.9 3.95 80.02 Thurston et al. 1981c
120

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Rainbow trout (9.5 g, 9.4 cm),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 9.01 14.5 2.51 69.50 Thurston et al. 1981c

Rainbow trout (juvenile),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 7.2 10 174 212.6 Wicks and Randall 2002

Rainbow trout

(40.0 g; swimming fish),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 6.97 16.6 32.38 31.56 Wicks et al. 2002

Rainbow trout

(40.0 g; resting fish),

Oncorhynchus mykiss

Ammonium 

chloride 4 d F,M 6.97 16.6 207 201.7 82.88 Wicks et al. 2002

Chinook salmon (1.0-7 g),

Oncorhynchus tshawytscha Ammonia 4 d S,M 7.96 7 28.03 111.6 Servizi and Gordon 1990

Chinook salmon

(14.4 g, 11.9 cm),

Oncorhynchus tshawytscha

Ammonium 

chloride 4 d F,U 7.87 13.5 18.47 62.29 Thurston and Meyn 1984

Chinook salmon

(15.3 g, 12.1 cm),

Oncorhynchus tshawytscha

Ammonium 

chloride 4 d F,U 7.82 12.2 27.23 83.90 Thurston and Meyn 1984

Chinook salmon

(18.1 g, 12.7 cm),

Oncorhynchus tshawytscha

Ammonium 

chloride 4 d F,U 7.84 12.3 24.74 79.02 82.39 99.15 Thurston and Meyn 1984

Topeka shiner (adult, 29 mo),

Notropis topeka

Ammonium 

chloride 4 d F,M 7.85 24.6 21.40 69.59 Adelman et al. 2009

Topeka shiner

(juvenile, 16 mo),

Notropis topeka

Ammonium 

chloride 4 d F,M 8.05 25.0 18.70 88.27 Adelman et al. 2009

Topeka shiner

(juvenile, 15 mo),

Notropis topeka

Ammonium 

chloride 4 d F,M 8.09 13.2 28.90 147.3 96.72 96.72 Adelman et al. 2009

Leopard frog (embryo),

Rana pipiens

Ammonium 

chloride 4 d F,M 8 20 31.04 133.3 Diamond et al. 1993

Leopard frog (8 d),

Rana pipiens

Ammonium 

chloride 4 d F,M 8 12 16.23 69.69 96.38 96.38 Diamond et al. 1993
121

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Long fingernailclam,

Musculium transversum

Ammonium 

chloride 4 d F,M 8.1 14.6 32.83 109.0 West 1985; Arthur et al. 1987

Long fingernailclam,

Musculium transversum

Ammonium 

chloride 4 d F,M 8.2 5.4 38.18 71.74 West 1985; Arthur et al. 1987

Long fingernailclam,

Musculium transversum

Ammonium 

chloride 4 d F,M 8.6 20.5 6.429 91.24 89.36 89.36 West 1985; Arthur et al. 1987

Smallmouth bass

(26-29 mm, 264-267 mg),

Micropterus dolomieu

Ammonium 

chloride 4 d F,M 7.16 22.3 123.4 144.3 Broderius et al. 1985

Smallmouth bass

(26-29 mm, 264-267 mg),

Micropterus dolomieu

Ammonium 

chloride 4 d F,M 6.53 22.3 359.9 269.2 Broderius et al. 1985

Smallmouth bass

(26-29 mm, 264-267 mg),

Micropterus dolomieu

Ammonium 

chloride 4 d F,M 7.74 22.3 39.3 105.2 Broderius et al. 1985

Smallmouth bass

(26-29 mm, 264-267 mg),

Micropterus dolomieu

Ammonium 

chloride 4 d F,M 8.71 22.3 7.56 126.0 150.6 Broderius et al. 1985

Largemouth bass

(0.086-0.322 g),

Micropterus salmoides

Ammonium 

chloride 4 d F,M 8.04 28 19.59 90.72 Roseboom and Richey 1977

Largemouth bass

(2.018-6.286 g),

Micropterus salmoides

Ammonium 

chloride 4 d F,M 7.96 22 20.48 81.56 86.02 Roseboom and Richey 1977

Guadalupe bass (6.5 g),

Micropterus treculii

Ammonium 

chloride 4 d S,M/ 8 22 12.7 54.52 54.52 89.06 Tomasso and Carmichael 1986

Great pond snail (25-30 mm),

Lymnaea stagnalis - 4 d F,M 7.9 11.5 50.33 88.62 88.62 88.62 Williams et al. 1986

Guppy (0.13 g, 2.03 cm),

Poecilia reticulata

Ammonium 

chloride 4 d S,U 7.5 27.55 5.929 10.76 Kumar and Krishnamoorthi 1983
122

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Guppy (8.0 mm),

Poecilia reticulata - 4 d S,U 7.22 25 129.4 161.8 Rubin and Elmaraghy 1976

Guppy (8.25(6.3-11.0) mm),

Poecilia reticulata - 4 d S,U 7.45 25 75.65 127.6 Rubin and Elmaraghy 1976

Guppy (8.70(6.8-10.6) mm),

Poecilia reticulata - 4 d S,U 7.45 25 82.95 139.9 74.66 74.66 Rubin and Elmaraghy 1976

Johnny darter (38 mm),

Etheostoma nigrum

Ammonium 

chloride 4 d F,M 7.9 20.6 28.9 103.0 Nimmo et al. 1989

Johnny darter (38 mm),

Etheostoma nigrum

Ammonium 

chloride 4 d F,M 8 20.1 24.61 105.7 Nimmo et al. 1989

Johnny darter (38 mm),

Etheostoma nigrum

Ammonium 

chloride 4 d F,M 8.2 6.2 6.937 43.72 Nimmo et al. 1989

Johnny darter (38 mm),

Etheostoma nigrum

Ammonium 

chloride 4 d F,M 8.1 5.8 11.47 59.57 Nimmo et al. 1989

Johnny darter (38 mm),

Etheostoma nigrum

Ammonium 

chloride 4 d F,M 8.1 5.8 13.46 69.93 Nimmo et al. 1989

Johnny darter (38 mm),

Etheostoma nigrum

Ammonium 

chloride 4 d F,M 8 20.1 15.63 67.08 71.45 Nimmo et al. 1989

Orangethroat darter,

Etheostoma spectabile

Ammonium 

chloride 4 d F,M 8.1 22 16.12 83.74 Hazel et al. 1979

Orangethroat darter,

Etheostoma spectabile

Ammonium 

chloride 4 d F,M 8.4 21 7.65 71.12 77.17 74.25 Hazel et al. 1979

Rio Grande silvery minnow

(3-5 d old),

Hybognathus amarus

Ammonium 

chloride 4 d R,M 8 25 16.9 72.55 72.55 72.55 Buhl 2002

Spring peeper (embryo),

Pseudacris crucifer

Ammonium 

chloride 4 d F,U 8 12 17.78 76.33 Diamond et al. 1993

Spring peeper,

Pseudacris crucifer

Ammonium 

chloride 4 d F,U 8 20 11.42 49.04 61.18 Diamond et al. 1993

Pacific tree frog (embryo),

Pseudacris regilla

Ammonium 

nitrate 4 d R,M 6.7 22 41.19 33.36 Schuytema and Nebeker 1999a
123

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Pacific tree frog (embryo),

Pseudacris regilla

Ammonium 

chloride 4 d R,M 6.7 22 60.44 48.95 Schuytema and Nebeker 1999a

Pacific tree frog (embryo),

Pseudacris regilla

Ammonium 

sulfate 4 d R,M 6.7 22 103.1 83.53 Schuytema and Nebeker 1999a

Pacific tree frog

(90 mg, Gosner Stage 26-27),

Pseudacris regilla

Nitric acid 

ammonium salt 4 d R,M 7.3 22 136.6 188.1 Schuytema and Nebeker 1999b

Pacific tree frog

(60 mg, Gosner Stage 26-27),

Pseudacris regilla

Ammonium 

sulfate 4 d R,M 7.3 22 116.4 160.2 83.71 71.56 Schuytema and Nebeker 1999b

Mucket (glochidia),

Actinonaias ligamentina

Ammonium 

chloride 1 d S,M 8.6 20 6.141c

83.61 Wang et al. 2007b

Mucket (glochidia),

Actinonaias ligamentina

Ammonium 

chloride 1 d S,M 8.4 20 8.099 c

75.29 Wang et al. 2007b

Mucket (glochidia),

Actinonaias ligamentina

Ammonium 

chloride 1 d S,M 8.3 20 5.073 c

38.84 Wang et al. 2007b

Mucket (glochidia),

Actinonaias ligamentina

Ammonium 

chloride 1 d S,M 8.3 20 8.900 c

68.13 63.89 Wang et al. 2007b

Pheasantshell (juvenile),

Actinonaias pectorosa

Ammonium 

chloride 4 d S,M 7.9 25 14.06 75.80 Keller 2000

Pheasantshell (juvenile),

Actinonaias pectorosa

Ammonium 

chloride 4 d S,M 7.95 25 14.08 83.30 79.46 71.25 Keller 2000

Giant floater mussel (adult),

Pyganodon grandis

Ammonium 

chloride 4 d S,M 7.71 25 18.84 72.49 Scheller 1997

Giant floater mussel (adult),

Pyganodon grandis

Ammonium 

chloride 4 d S,M 7.5 25 25.13 69.02 70.73 70.73 Scheller 1997

Shortnose sucker (0.53-2.00 g),

Chasmistes brevirostris

Ammonium 

chloride 4 d F,M 8 20 11.42 49.04 Saiki et al. 1999

Shortnose sucker,

Chasmistes brevirostris

Ammonium 

chloride 4 d F,M 8 20 22.85 98.09 69.36 69.36 Saiki et al. 1999
124

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Pagoda hornsnail (adult),

Pleurocera uncialis

Ammonium 

chloride 4 d R,M 8.1 22 11.18 68.54 68.54 68.54 Goudreau et al. 1993

Golden shiner,

Notemigonus crysoleucas

Ammonium 

chloride 4 d S,M 7.5 19.6 89.61 162.6 EA Engineering 1985

Golden shiner,

Notemigonus crysoleucas

Ammonium 

chloride 4 d S,M 7.55 19.5 73.85 144.6 EA Engineering 1985

Golden shiner (8.7 g),

Notemigonus crysoleucas

Ammonium 

chloride 4 d F,M 7.5 24.5 34.73 63.02 63.02 63.02 Swigert and Spacie 1983

Pebblesnail (1.8 mm),

Fluminicola sp.

Ammonium 

chloride 4 d F,M 8.25 20.2 >8.801 >62.15 >62.15 >62.15 Besser 2011

Lost River sucker (0.49-0.80 g),

Deltistes luxatus

Ammonium 

chloride 4 d F,M 8 20 16.81 72.18 Saiki et al. 1999

Lost River sucker (larvae),

Deltistes luxatus

Ammonium 

chloride 4 d F,M 8 20 10.35 44.42 56.62 56.62 Saiki et al. 1999

Mountain whitefish

(177 g, 27.0 cm),

Prosopium williamsoni

Ammonium 

chloride 4 d F,U 7.68 12.1 11.3 27.31 Thurston and Meyn 1984

Mountain whitefish

(56.9 g, 19.1 cm),

Prosopium williamsoni

Ammonium 

chloride 4 d F,U 7.84 12.4 25.47 81.35 Thurston and Meyn 1984

Mountain whitefish

(63.0 g, 20.4 cm),

Prosopium williamsoni

Ammonium 

chloride 4 d F,U 7.8 12.3 21.2 63.04 51.93 51.93 Thurston and Meyn 1984

Atlantic pigtoe (glochidia),

Fusconaia masoni

Ammonium 

chloride 6 h S,M 7.6 24.9 15.9 47.40 47.40 47.40 Black 2001

Pondshell mussel (juvenile),

Utterbackia imbecillis

Ammonium 

chloride 4 d S,M 7.9 24 8.235 40.87 Keller 2000

Pondshell mussel (juvenile),

Utterbackia imbecillis

Ammonium 

chloride 4 d S,M 8.35 25 3.269 41.75 Keller 2000
125

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Pondshell mussel (juvenile),

Utterbackia imbecillis

Ammonium 

chloride 4 d S,M 7.9 25 9.355 50.45 Keller 2000

Pondshell mussel 

(8 d old juvenile),

Utterbackia imbecillis

Ammonium 

chloride 4 d R,M 7.8 24 14.29 59.19 Wade et al. 1992

Pondshell mussel 

(<2 d old juvenile),

Utterbackia imbecillis

Ammonium 

chloride 4 d R,M 8.16 25 5.254 46.38 Black 2001

Pondshell mussel 

(<2 d old juvenile),

Utterbackia imbecillis

Ammonium 

chloride 4 d R,M 8.17 25 5.781 52.03 Black 2001

Pondshell mussel 

(<2 d old juvenile),

Utterbackia imbecillis

Ammonium 

chloride 4 d R,M 8.29 25 8.845 100.5 Black 2001

Pondshell mussel 

(<2 d old juvenile),

Utterbackia imbecillis

Ammonium 

chloride 4 d R,M 8 25.1 2.734 17.91 Black 2001

Pondshell mussel (glochidia),

Utterbackia imbecillis

Ammonium 

chloride 1 d S,M 8.02 25 7.395 49.90 46.93 46.93 Black 2001

Pink mucket 

(2 mo old juvenile),

Lampsilis abrupta

Ammonium 

chloride 4 d R,M 8.3 20 1.921d

14.71 Wang et al. 2007b

Pink mucket 

(2 mo old juvenile),

Lampsilis abrupta

Ammonium 

chloride 4 d F,M 8.4 20 2.8 26.03 26.03 Wang et al. 2007a

Plain pocketbook 

(3-5 d old juvenile),

Lampsilis cardium

Ammonium 

chloride 4 d S,M 8.2 20.5 23.50e

154.4 Newton et al. 2003

Plain pocketbook 

(3-5 d old juvenile),

Lampsilis cardium

Ammonium 

chloride 4 d S,M 8.2 21.2 23.70e

165.0 Newton et al. 2003

Plain pocketbook 

(1-2 d old juvenile),

Lampsilis cardium

Ammonium 

chloride 4 d F,M 7.6 21.2 23.1 54.07 Newton and Bartsch 2007
126

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Plain pocketbook 

(1-2 d old juvenile),

Lampsilis cardium

Ammonium 

chloride 4 d F,M 7.1 21.2 38.9 47.19 50.51 Newton and Bartsch 2007

Wavy-rayed lampmussel 

(2-5 d old juvenile),

Lampsilis fasciola

Ammonium 

chloride 4 d R,M 7.83 12.6 14.9 25.31 Mummert et al. 2003

Wavy-rayed lampmussel 

(<5 d old juvenile),

Lampsilis fasciola

Ammonium 

chloride 4 d R,M 8.5 20 6.179d

69.63 Wang et al. 2007b

Wavy-rayed lampmussel 

(glochidia),

Lampsilis fasciola

Ammonium 

chloride 1 d S,M 8.3 20 7.743 c

59.28 Wang et al. 2007b

Wavy-rayed lampmussel 

(glochidia),

Lampsilis fasciola

Ammonium 

chloride 1 d S,M 8.4 20 5.518 c

51.30 48.11 Wang et al. 2007b

Higgin's eye 

(1-2 d old juvenile),

Lampsilis higginsii

Ammonium 

chloride 4 d F,M 7.6 21.2 19.5 45.64 Newton and Bartsch 2007

Higgin's eye 

(1-2 d old juvenile),

Lampsilis higginsii

Ammonium 

chloride 4 d F,M 7.1 21.2 31.7 38.46 41.90 Newton and Bartsch 2007

Neosho mucket 

(<5 d old juvenile),

Lampsilis rafinesqueana

Ammonium 

chloride 4 d R,M 8.3 20 9.185d

70.31 Wang et al. 2007b

Neosho mucket 

(<5 d old juvenile),

Lampsilis rafinesqueana

Ammonium 

chloride 4 d R,M 8.4 20 9.269d

86.17 Wang et al. 2007b

Neosho mucket (glochidia),

Lampsilis rafinesqueana

Ammonium 

chloride 1 d S,M 8.3 20 7.387 c

56.55 69.97 Wang et al. 2007b

Fatmucket (juvenile),

Lampsilis siliquoidea

Ammonium 

chloride 4 d S,M 8.3 24 1.275 13.60 Myers-Kinzie 1998
127

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Fatmucket (3 mo old juvenile),

Lampsilis siliquoidea

Ammonium 

chloride,

ammonium 

hydroxide

4 d F,M 8.35 20 8.80 74.25 Miao et al. 2010

Fatmucket (2 mo old juvenile),

Lampsilis siliquoidea

Ammonium 

chloride 4 d R,M 8.1 20 4.092d

21.26 Wang et al. 2007b

Fatmucket (2 mo old juvenile),

Lampsilis siliquoidea

Ammonium 

chloride 4 d F,M 8.2 20 4.6 28.99 Wang et al. 2007a

Fatmucket (7 d old juvenile),

Lampsilis siliquoidea

Ammonium 

chloride,

ammonium 

hydroxide

4 d F,M 7.6 20.5 11 24.30 Wang et al. 2008

Fatmucket (7 d old juvenile),

Lampsilis siliquoidea

Ammonium 

chloride,

ammonium 

hydroxide

4 d F,M 8.1 20.6 5.2 28.39 Wang et al. 2008

Fatmucket (7 d old juvenile),

Lampsilis siliquoidea

Ammonium 

chloride,

ammonium 

hydroxide

4 d F,M 8.5 20.6 3.4 40.27 Wang et al. 2008

Fatmucket (7 d old juvenile),

Lampsilis siliquoidea

Ammonium 

chloride,

ammonium 

hydroxide

4 d F,M 9 20.6 0.96 27.51 Wang et al. 2008

Fatmucket (7 d old juvenile),

Lampsilis siliquoidea

Ammonium 

chloride,

ammonium 

hydroxide

4 d F,M 6.6 19.6 88 65.59 Wang et al. 2008

Fatmucket (7 d old juvenile),

Lampsilis siliquoidea

Ammonium 

chloride,

ammonium 

hydroxide

4 d F,M 8.1 19.4 11 54.37 Wang et al. 2008

Fatmucket (<5 d old juvenile),

Lampsilis siliquoidea

Ammonium 

chloride 4 d R,M 8.5 20 8.350d

94.09 Wang et al. 2007b

Fatmucket (glochidia),

Lampsilis siliquoidea

Ammonium 

chloride 1 d S,M 8.4 20 9.790 c

91.01 Wang et al. 2007b
128

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Fatmucket (glochidia),

Lampsilis siliquoidea

Ammonium 

chloride 1 d S,M 8.2 20 13.35 c

84.14 Wang et al. 2007b

Fatmucket (glochidia),

Lampsilis siliquoidea

Ammonium 

chloride 1 d S,M 8.4 20 11.57 c

107.6 Wang et al. 2007b

Fatmucket (glochidia),

Lampsilis siliquoidea

Ammonium 

chloride 1 d S,M 8.5 20 >14.24 c

160.5 Wang et al. 2007b

Fatmucket (glochidia),

Lampsilis siliquoidea

Ammonium 

chloride 1 d S,M 8.3 20 6.497 c

49.74 Wang et al. 2007b

Fatmucket (glochidia),

Lampsilis siliquoidea

Ammonium 

chloride 1 d S,M 8.3 20 8.772 c

66.77 55.42 46.63 Wang et al. 2007b

Rainbow mussel 

(2 mo old juvenile),

Villosa iris

Ammonium 

chloride 4 d R,M 8.4 20 2.505d

23.29 Wang et al. 2007b

Rainbow mussel 

(2 mo old juvenile),

Villosa iris

Ammonium 

chloride 4 d R,M 8.3 20 8.935d

68.40 Wang et al. 2007b

Rainbow mussel 

(5 d old juvenile),

Villosa iris

Ammonium 

chloride 4 d S,M 8.18 25 7.81 71.66 Scheller 1997

Rainbow mussel 

(<5 d old juvenile),

Villosa iris

Ammonium 

chloride 4 d R,M 8.1 20 5.261d

27.33 Wang et al. 2007b

Rainbow mussel 

(2-5 d old juvenile),

Villosa iris

Ammonium 

chloride 4 d R,M 7.29 12.6 20.6 15.17 Mummert et al. 2003

Rainbow mussel 

(<3 d old juvenile),

Villosa iris

Ammonium 

chloride 4 d S,M 8.18 25 7.07 64.87 Scheller 1997

Rainbow mussel 

(< 24 h old glochidia),

Villosa iris

Ammonium 

chloride 1 d S,M 7.94 20.0 3.290 12.62 Scheller 1997

Rainbow mussel (glochidia),

Villosa iris

Ammonium 

chloride 1 d S,M 8.4 20 10.68 c

99.28 Wang et al. 2007b
129

Appendix A. Acute Toxicity of Ammonia to Aquatic Animals

Species Chemical Name Duration MethodsapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Total Ammoniab

(mg TAN/L)

adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

SMAV

(mg 

TAN/L)

GMAV

(mg 

TAN/L) Reference

Rainbow mussel 

(<1 h old glochidia),

Villosa iris

Ammonium 

chloride 1 d R,M 8.1 22 3.570 21.89 Goudreau et al. 1993

Rainbow mussel 

(<1 h old glochidia),

Villosa iris

Ammonium 

chloride 1 d R,M 8.1 22 4.278 26.23 34.23 34.23 Goudreau et al. 1993

Oyster mussel 

(<5 d old juvenile),

Epioblasma capsaeformis

Ammonium 

chloride 4 d R,M 8.5 20 4.760d

53.63 Wang et al. 2007b

Oyster mussel (glochidia),

Epioblasma capsaeformis

Ammonium 

chloride 6 h R,M 8.5 20 5.0 c

17.81 Wang et al. 2007b

Oyster mussel (glochidia),

Epioblasma capsaeformis

Ammonium 

chloride 6 h R,M 8.5 20 3.4 c

31.61 31.14 31.14 Wang et al. 2007b

Green floater (<2 d old 

juvenile),

Lasmigona subviridis

Ammonium 

chloride 4 d R,M 7.73 24 6.613 24.24 Black 2001

Green floater (<2 d old 

juvenile),

Lasmigona subviridis

Ammonium 

chloride 4 d R,M 7.73 24 6.613 24.24 Black 2001

Green floater (<2 d old 

juvenile),

Lasmigona subviridis

Ammonium 

chloride 4 d R,M 7.92 24.8 3.969 21.84 23.41 23.41 Black 2001

Ellipse (glochidia),

Venustaconcha ellipsiformis

Ammonium 

chloride 1 d S,M 8.1 20 4.550 c

23.12 23.12 23.12 Wang et al. 2007b

a

S = static, R = renewal, F = flow-through, and NR= not reported (uncertain) exposure types; M = measured and U = unmeasured tests.

b Acute values are normalized to pH 7 (all organisms) and temperature 20°C (invertebrates) as per the equations provided in this document (see also 1999 AWQC document for the basis of 

the pH- and temperature-dependence of ammonia toxicity and Appendix D for an example calculation).

c The EC50s reported in this study were based on nominal concentrations. Percent nominal concentrations of measured ammonia concentrations on exposure days 0 and 2 declined from 104 

to 44. EC50s based on measured concentrations were estimated from the reported EC50s based on nominal concentrations by multiplying by 0.890 for the 24 hr test; this factor is the average 

of the percent nominal concentrations of measured concentrations from ammonia measurements made on exposure day 0 (i.e., 104) and estimated for day 1 (i.e, 74) of the study.
130

d The EC50s reported in this study were based on nominal concentrations. Percent nominal concentrations of measured ammonia concentrations on exposure days 0 and 4 declined from 104 

to 63. EC50s based on measured concentrations were estimated from the reported EC50s based on nominal concentrations by multiplying by 0.835 or the average of the percent nominal 

concentrations of measured concentrations from ammonia measurements made on exposure days 0 and 4 in the study. 

e EC50 values based on sediment porewater concentrations. Note: these EC50s were not used to calculate the SMAV for the species.

f This small subset of LC50s for adult rainbow trout from Thurston and Russo (1983) was used as the basis for the FAV calculated in the 1999 AWQC document. The FAV in the 1999 

AWQC document of 11.23 mg TAN/L at pH 8 was lowered to the geometric mean of these five LC50 values at the time in order to protect large rainbow trout, which were shown to be 

measurably more sensitive than other life stages. The FAV prior to adjusting it to protect the commercially and recreationally important adult rainbow trout was calculated to be 14.32 mg 

TAN/L (CMC = 7.2 mg TAN/L) at pH 8. This FAV based on protection of adult rainbow trout at pH 7 is 48.21 mg TAN/L (see Table 7 in this document). Because several equivalent LC50s 

representing different ages and life-stages have been added to the current (updated) acute criteria dataset, it no longer seems appropriate to lower the SMAV for rainbow trout based on only 

these five LC50s considering the several other additional acute values which now exist. 

Note: Each SMAV was calculated from the associated bold-face number(s) in the preceding column.
131

Appendix B. Chronic Toxicity of Ammonia to Aquatic Animals.

Appendix B. Chronic Toxicity of Ammonia to Aquatic Animals

Species Test and Effect pH

Temp.

( ̊C)

Total

Ammonia

(mg 

TAN/L)

Chronic valuea

Adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

(mg TAN/L)

SMCV

(mg 

TAN/L)

GMCV

(mg 

TAN/L) Reference

Stonefly,

Pteronarcella badia 30-d Juv Survival 8.04 12.1 133.8 207.0 Thurston et al. 1984b

Stonefly,

Pteronarcella badia 24-d Juv Survival 7.81 13.2 21.66 26.27 73.74 73.74 Thurston et al. 1984b

Water flea,

Ceriodaphnia acanthina 7-d LC Reproduction 7.15 24.5 44.90 64.10 64.10 Mount 1982

Water flea,

Ceriodaphnia dubia 7-d LC Reproduction 7.80 25.0 15.20 38.96 Nimmo et al. 1989

Water flea,

Ceriodaphnia dubia 7-d LC Reproduction 8.57 26.0 5.800 52.15 45.08 53.75 Willingham 1987

Water flea,

Daphnia magna 21-d LC Reproduction 8.45 19.8 7.370 36.27 Gersich et al. 1985

Water flea,

Daphnia magna 21-d LC Reproduction 7.92 20.1 21.70 47.40 41.46 41.46 Reinbold and Pescitelli 1982a

Amphipod,

Hyalella azteca 28-d PLC Biomass 8.04 25.0 8.207 29.17 29.17 29.17 Borgmann 1994

Channel catfish,

Ictalurus punctatus 30-d ELS Weight 7.80 25.8 12.20 22.66 Reinbold and Pescitelli 1982a

Channel catfish,

Ictalurus punctatus 30-d Juv Survival 8.35 27.9 5.020 21.15 Colt and Tchobanoglous 1978

Channel catfish,

Ictalurus punctatus 30-d ELS Biomass 7.76 26.9 11.50 20.35 21.36 21.36 Swigert and Spacie 1983

Northern pike (fertilized),

Esox lucius 52-d ELS Biomass 7.62 8.70 13.44 20.38 20.38 20.38 Harrahy et al. 2004

Common carp (fertilized),

Cyprinus carpio 28-d ELS Weight 7.85 23.0 8.360 16.53 16.53 16.53 Mallet and Sims 1994
132

Appendix B. Chronic Toxicity of Ammonia to Aquatic Animals

Species Test and Effect pH

Temp.

( ̊C)

Total

Ammonia

(mg 

TAN/L)

Chronic valuea

Adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

(mg TAN/L)

SMCV

(mg 

TAN/L)

GMCV

(mg 

TAN/L) Reference

Lahontan cutthroat trout (fertilized),

Oncorhynchus clarkii henshawi 103-d ELS Survival 7.57 13.7 17.89 25.83 25.83 Koch et al. 1980

Rainbow trout (fertilized),

Oncorhynchus mykiss 42-d ELS Survival 7.50 10.0 <33.6 <45.5 Burkhalter and Kaya 1977

Rainbow trout,

Oncorhynchus mykiss 72-d ELS Survival 7.40 14.5 2.600 3.246 Calamari et al. 1977, 1981

Rainbow trout (fertilized),

Oncorhynchus mykiss 73-d ELS Survival 7.52 14.9 <2.55 <3.515 Solbe and Shurben 1989

Rainbow trout,

Oncorhynchus mykiss 5-year LC 7.70 7.5-10.5 >6.71 >11.08 Thurston et al. 1984a

Rainbow trout,

Oncorhynchus mykiss 90-d ELS Survival 7.75 11.4 8.919 15.60 6.663 Brinkman et al. 2009

Sockeye salmon,

Oncorhynchus nerka

62-d Embryos 

Hatchability 8.42 10.0 <2.13 <10.09 10.09 12.02 Rankin 1979

White sucker (3 d old embryo),

Catostomus commersonii 30-d ELS Biomass 8.32 18.6 2.900 >11.62 11.62 11.62 Reinbold and Pescitelli 1982a

Smallmouth bass,

Micropterus dolomieu 32-d ELS Biomass 6.60 22.3 9.610 8.650 Broderius et al. 1985

Smallmouth bass,

Micropterus dolomieu 32-d ELS Biomass 7.25 22.3 8.620 9.726 Broderius et al. 1985

Smallmouth bass,

Micropterus dolomieu 32-d ELS Biomass 7.83 22.3 8.180 15.77 Broderius et al. 1985

Smallmouth bass,

Micropterus dolomieu 32-d ELS Biomass 8.68 22.3 1.540 11.31 11.07 11.07 Broderius et al. 1985

Fathead minnow (embryo-larvae),

Pimephales promelas 28-d ELS Survival 8.00 24.8 5.120 12.43 Mayes et al. 1986

Fathead minnow (embryo-larvae),

Pimephales promelas 32-d ELS Biomass 7.95 25.5 7.457 16.87 Adelman et al. 2009

Fathead minnow,

Pimephales promelas 30-d ELS Biomass 7.82 25.1 3.730 7.101 Swigert and Spacie 1983
133

Appendix B. Chronic Toxicity of Ammonia to Aquatic Animals

Species Test and Effect pH

Temp.

( ̊C)

Total

Ammonia

(mg 

TAN/L)

Chronic valuea

Adjusted to pH 7

(all organisms)

and 20°C

(invertebrates)

(mg TAN/L)

SMCV

(mg 

TAN/L)

GMCV

(mg 

TAN/L) Reference

Fathead minnow,

Pimephales promelas LC Hatchability 8.00 24.2 1.970 4.784 9.187 9.187 Thurston et al. 1986

Pebblesnail (1.81 mm, juvenile),

Fluminicola sp.

28-d Juv Change in 

Length 8.22 20.1 2.281 7.828 7.828 7.828 Besser 2011

Long fingernailclam,

Musculium transversum 42-d Juv Survival 8.15 23.5 5.820 22.21 Anderson et al. 1978

Long fingernailclam,

Musculium transversum 42-d Juv Survival 7.80 21.8 1.230 2.565 7.547 7.547 Sparks and Sandusky 1981

Green sunfish,

Lepomis cyanellus 30-d ELS Biomass 7.90 22.0 5.610 11.85 McCormick et al. 1984

Green sunfish,

Lepomis cyanellus 30-d ELS Survival 8.16 25.4 5.840 18.06 14.63 Reinbold and Pescitelli 1982a

Bluegill,

Lepomis macrochirus 30-d ELS Biomass 7.76 22.5 1.850 3.273 3.273 6.920 Smith et al. 1984

Rainbow mussel (2 mo old juvenile),

Villosa iris 28-d Juv Survival 8.20 20.0 1.063 3.501 3.501 3.501 Wang et al. 2007a

Fatmucket (2 mo old juvenile),

Lampsilis siliquoidea 28-d Juv Survival 8.25 20.0 0.8988 3.211 3.211 Wang et al. 20011

Wavy-rayed lamp mussel

(2 mo old juvenile),

Lampsilis fasciola

28-d Juv Survival 8.20 20.0 0.4272 1.408 1.408 2.126 Wang et al. 2007a

a The chronic value is an EC20 value calculated using EPA’s TRAP (Versions 1.0 or 1.21a). Note: all chronic values were normalized to pH 7 (all organisms) and 20°C 

(invertebrates) as per the equations provided in this document (see also 1999 AWQC document for the basis of the pH- and temperature-dependence of ammonia toxicity and 

Appendix E for an example calculation).

Note: Each SMCV was calculated from the associated bold-face number(s) in the preceding column.
134

Appendix C. Other Chronic Ammonia Toxicity Data.

Appendix C. Other Chronic Ammonia Toxicity Data

Species Test and Effect MethodapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Chronic value

Adjusted to pH 7

(all organisms) and

20°C (invertebrates)

(mg TAN/L) Reference

FRESHWATER INVERTEBRATES

Pulmonate pondsnail

(<1 wk post hatch),

Lymnaea stagnalis

28-d NOEC -

Growth F,M 8.25 20.1 >8.00 >28.76 Besser et al. 2009

Pulmonate pondsnail

(<1 wk post-hatch),

Lymnaea stagnalis

28-d NOEC -

Survival F,M 8.25 20.1 >8.00 >28.76 Besser et al. 2009

Idaho springsnail

(7-9 and 11-13 wk post hatch juvenile),

Pyrgulopsis idahoensis

28-d NOEC -

Growth F,M 8.25 20.1 >8.00 >28.76 Besser et al. 2009

Idaho springsnail

(7-9 and 11-13 wk post hatch juvenile),

Pyrgulopsis idahoensis

28-d EC20 - Survival F,M 8.25 20.1 0.480 1.726 Besser et al. 2009

Idaho springsnail

(mixed-aged, adults),

Pyrgulopsis idahoensis

28-d EC20 - Survival F,M 8.26 20.8 3.24 12.39b Besser et al. 2009

Pebblesnail (mixed-aged, field collected),

Fluminicola sp.

28-d EC20 - Survival F,M 8.26 20.8 1.02 3.900c Besser et al. 2009

Pebblesnail (small, field collected),

Fluminicola sp.

28-d MATC -

Survival F,M 8.19 20.1 2.75 8.977d Besser 2011

Ozark springsnail

(mixed age, field collected),

Fontigens aldrichi

28-d EC20 - Survival F,M 8.26 20.8 0.61 2.332b Besser et al. 2009

Bliss Rapids snail

(mixed age, field collected),

Taylorconcha serpenticola

28-d EC20 - Survival F,M 8.26 20.8 3.42 13.08b Besser et al. 2009
135

Appendix C. Other Chronic Ammonia Toxicity Data

Species Test and Effect MethodapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Chronic value

Adjusted to pH 7

(all organisms) and

20°C (invertebrates)

(mg TAN/L) Reference

Silty hornsnail

(mixed age, mature and field collected),

Pleurocera canaliculata

28-d EC20 -

Survival; 

(Alt Effect Conc.)

F,M 8.15 24.7 0.45

(≤1.86)

1.845

(≤7.667)b, e GLEC 2011

Wavy-rayed lamp mussel

(2 mo old juvenile),

Lampsilis fasciola

28-d IC25 - Growth F,M 8.20 20.0 0.5700 1.878 Wang et al. 2007a

Fatmucket (2 mo old juvenile),

Lampsilis siliquoidea 28-d IC25 - Growth F,M 8.20 20.0 0.4400 1.450 Wang et al. 2007a

Rainbow mussel (2 mo old juvenile),

Villosa iris 28-d IC25 - Growth F,M 8.20 20.0 0.7300 2.406 Wang et al. 2007a

Water flea, (<24 hr),

Ceriodaphnia dubia

7-d; 

3 broods in control 

IC25 Reproduction

R,U 7.90 25.0 1.300 3.790 Dwyer et al. 2005

FRESHWATER VERTEBRATES

Cutthroat trout (3.3 g),

Oncorhynchus clarkii 29-d LC50 F,M 7.80 12.4 21.60 40.11 Thurston et al. 1978

Cutthroat trout (3.4 g),

Oncorhynchus clarkii 29-d LC50 F,M 7.78 12.2 21.40 38.78 Thurston et al. 1978

Cutthroat trout (1.0 g),

Oncorhynchus clarkii 36-d LC50 F,M 7.81 13.1 30.80 57.91 Thurston et al. 1978

Cutthroat trout (1.0 g),

Oncorhynchus clarkii 36-d LC50 F,M 7.80 12.8 32.20 59.79 Thurston et al. 1978

Atlantic salmon,

Salmo salar

105-d Juv NOEC -

Survival F,M 6.84 12.1 >32.29 >30.64 Kolarevic et al. 2012

Lake trout, siscowet,

Salvelinus namaycush

60-d LOECWeight gain F,M 8.02 11.6 6.440 16.10 Beamish and Tandler 1990

Brook trout (juvenile),

Salvelinus fontinalis

4-d Juv LOEC -

Swimming Perf F,M 9.10 15.0 0.7765 10.86 Tudorache et al. 2010

Bonytail chub

(2 and 7 d post hatch),

Gila elegans

7-d IC25 - Growth R,U 7.90 25.0 11.00 23.24 Dwyer et al. 2005
136

Appendix C. Other Chronic Ammonia Toxicity Data

Species Test and Effect MethodapH

Temp.

( ̊C)

Total 

Ammonia

(mg 

TAN/L)

Chronic value

Adjusted to pH 7

(all organisms) and

20°C (invertebrates)

(mg TAN/L) Reference

Spotfin chub (<24 hr),

Erimonax monachus 7-d IC25 - Growth R,U 7.90 25.0 15.80 33.37 Dwyer et al. 2005

Cape Fear shiner (<24 hr),

Notropis mekistocholas 7-d IC25 - Growth R,U 7.90 25.0 8.800 18.59 Dwyer et al. 2005

Topeka shiner (adult),

Notropis topeka 30-d EC20 - Survival F,M 7.94 23.9 10.85 24.21 Adelman et al. 2009

Topeka shiner (juvenile, 11 mo),

Notropis topeka 30-d EC20 - SGR F,M 8.07 12.4 6.483 17.45 Adelman et al. 2009

Gila topminnow (<24, 48 and 72 hr),

Poeciliopsis occidentalis 7-d IC25 - Growth R,U 7.90 25.0 24.10 50.91 Dwyer et al. 2005

Fathead minnow (<24 hr),

Pimephales promelas 7-d IC25 - Growth R,U 7.90 25.0 7.200 15.21 Dwyer et al. 2005

Fathead minnow (4 d post hatch),

Pimephales promelas

28-d LOECSurvival R,M 8.25 19.9 9.160 32.71 Fairchild et al. 2005

Colorado pikeminnow

(5 and 6-d post hatch),

Ptychocheilus lucius

7-d IC25 - Growth R,U 7.90 25.0 8.900 18.80 Dwyer et al. 2005

Colorado pikeminnow (juvenile, 8 d),

Ptychocheilus lucius 28-d LOEC- Growth R,M 8.23 19.9 8.600 29.75 Fairchild et al. 2005

Razorback sucker (7 d post hatch),

Xyrauchen texanus 7-d IC25 - Growth R,U 7.90 25.0 13.40 28.30 Dwyer et al. 2005

Razorback sucker (9 d),

Xyrauchen texanus

28-d LOECSurvival R,M 8.24 19.9 13.25 46.58 Fairchild et al. 2005

Lost River sucker (late-stage larva),

Deltistes luxatus

30-d LOECSurvival F,M 9.43 22.3 1.230 25.31 Meyer and Hansen 2002

Green frog (Stage 24-26),

Rana clamitans

103-d NOECGrowth R,M 8.70 24.0 >2.20 >16.74 Jofre and Karasov 1999

a

R = renewal and F = flow-through exposure types; M = measured and U = unmeasured tests.

b Not used in the calculation of the SMCV because of the uncertainty of the chronic value, but included here as weight of evidence supporting the sensitivity of non-pulmonate 

snail species in general as determined by 28-day toxicity tests (see Additional 28-day Toxicity test Data for Freshwater Snails in Appendix I for more detail).

c Not used in the calculation of the SMCV because of the uncertainty of the chronic value, but included here as weight of evidence supporting the sensitivity of non-pulmonate 

snail species in general as determined by 28-day toxicity tests (see Chronic Toxicity Test Data: 28-day Tests with Juvenile and Adult Pebblesnails in Appendix H for more detail).
137

d Not used in the calculation of the SMCV because of low control survival (75 percent) for this size class.

e Value represents a 28-day ammonia survival effects concentration used in place of the EC20 due to the high degree of temporal variability in measured total ammonia 

concentrations in the test, as well as the unequal response among test replicates near this concentration (see Additional 28-day Toxicity test Data for Freshwater Snails in Appendix 

I for more detail).
138

Appendix D. Conversion of Acute Results of Toxicity Tests.

All of the ammonia acute values (LC50s and EC50s) in Appendix A of this document were 

converted to TAN acute values using the reported temperatures and pHs, and using the pKa 

relationship from Emerson et al. (1975). Conversions were dependent on the form of ammonia 

the acute values were expressed, e.g., unionized ammonia (UIA), unionized ammonia expressed 

as nitrogen (UIA-N), total ammonia (TA) and total ammonia nitrogen (TAN). After acute values 

were converted to TAN they were then normalized to pH 7 using the pH relationship developed 

in the 1999 AWQC document. Following the adjustment to pH 7, the TAN acute values were 

further normalized to a temperature of 20

°C for invertebrates only, following recommendations 

in the 1999 AWQC document. It is worth noting here that while the relationship between pH 

and ammonia toxicity was first addressed in the 1985 criteria document, it was not fully 

developed until the 1999 AWQC update document. Detailed information regarding the 

development and parameterization of the pH-ammonia toxicity equations (acute and chronic) can 

be found in the 1999 AWQC document (pH-Dependence of Ammonia Toxicity – U.S. EPA 

1999). In contrast to the pH-toxicity relationship, which applies to both vertebrates and 

invertebrates, the temperature-ammonia toxicity relationship only applies to invertebrates. Based 

on the results of the 1999 reanalysis of this relationship, it was determined that ammonia toxicity 

for invertebrates decreases with decreasing temperature to a temperature of approximately 7°C, 

below which the relationship ends (U.S. EPA 1999).

The conversion procedure for acute toxicity values is illustrated here using the data for 

the flatworm, Dendrocoelum lacteum, which is the first species listed in Table 1 in the 

1984/1985 criteria document and was the species chosen to illustrate the conversion procedure in 

Appendix 3 of the 1999 AWQC document:

Acute value (AV) = 1.40 mg unionized ammonia (UIA) or NH3/L

Test pH = 8.20

Test Temperature = 18.0°C
139

Step 1.

Equation 3 in the 1999 criterion document, and the Emerson et al. (1975) equation from 

page 7 of this document, is used to calculate the pKa at 18 °C:

pKa = 9.464905

Step 2.

The AV in terms of total ammonia (TA) is calculated as:

[NH3]/[NH+

4] = 10(pH-pK) = 0.0543369

Step 3.

The Wood (1993) equation from page 7 (Equation 2 in the 1999 AWQC document) is 

rearranged to obtain the acute value for TA:

TA = [NH3] + [NH+

4] = [NH3] + [NH3]/(10(pH-pKa)

)

TA = [NH3] + [NH+

4] = [NH3] + [NH3]/0.0543369

= 27.1652 mg TA/L

Step 4.

The AV for TA is converted to the AV for TAN (AVt) as follows:

AVt/AV = (14 mg TAN/mmol) / (17 mg TA/mmol) = 14/17

AVt = (27.1652 mg TA/L) x (14 mg TAN/17 mg TA)

= 22.3713 mg TAN/L
140

Step 5.

The AV in terms of TAN, or AVt, is converted from test pH 8.2 to pH 7 using the 

equation for describing the pH-dependence of acute values (modified from Equation 11 

in the 1999 AWQC document for normalization to pH 7)

2

:

 

 

(

 

 

 

 )

AVt,7 = (AVt)/(0.158673) = 140.990 mg N/L

Step 6. (temperature adjustment for invertebrates only)

The AV in terms of TAN at pH 7, or AVt,7, is converted from this concentration at test 

temperature to a standard test temperature of 20

°C using the equation shown below 

(Equation 5 in the 1999 AWQC document)

3

:

log(AVt,7,20) = log(AVt,7) - [-0.036(18°C - 20

°C)]

= 119.451 mg N/L

Because this is the only species in this genus for which data are in Table 1 in the 1984/1985 

criteria document, 119.5 mg TAN/L is the GMAV for the genus Dendrocoelum in Table 3 of this 

update document.

 

2 The equation provided here should be applicable from pH 6 to 9, although uncertainty might exist at the lower end 

of this range for certain species. Extrapolation below pH 6 is not advisable because of the increasing scatter of the 

data from the common regression line at lower pH, and extrapolation above pH 9 is not advisable because of 

inadequate knowledge about the effect of the inhibition of ammonia excretion at high pH on results of toxicity tests 

(Russo et al. 1988).

3 Note: Based on the 1999 reanalysis of the relationship between temperature and ammonia toxicity, when test 

temperature is less than 7°C, T should be set equal to 7, to reflect the plateau of the temperature-toxicity relationship 

at these temperatures.
141

Appendix E. Conversion of Chronic Results of Toxicity Tests.

As in the previous appendix with the acute results of toxicity tests, all of the ammonia 

chronic values (EC20s) in Appendix B of this document were first converted to TAN at test 

temperature and pH using the pKa relationship from Emerson et al. (1975). Once all the chronic 

values were converted to total ammonia nitrogen, these values were then adjusted to pH 7 using 

the pH relationship developed in the 1999 AWQC document. After the adjustment to pH 7, the 

TAN chronic values were further normalized to a temperature of 20

°C for invertebrates only, as 

per the recommendations in the 1999 AWQC document. The conversion procedure is illustrated 

here using the data for the amphipod species Hyalella azteca.

Chronic value (CV) = EC20 of 8.207 mg TAN/L

Test pH = 8.04

Test Temperature = 25.0°C

Steps 1 through 4.

(Not required in this case as CV is already expressed in terms of TAN. For more details 

regarding these steps, see Appendix D).

Step 5.

The CV in terms of TAN, or CVt, is converted from test pH 8.04 to pH 7 using the 

equation for describing the pH dependence of chronic values (modified from Equation 12 

in the 1999 AWQC document for normalization to pH 7)

4

:

 

 

(

 

 

 

 )

 

4

See footnote 3 in Appendix D.
142

CVt,7 = (CVt)/(0.38855) = 21.13 mg TAN/L

Step 6. (Temperature adjustment for invertebrates only)

The CV in terms of TAN at pH 7, or CVt,7, is converted from this concentration at test 

temperature to a standard test temperature of 20°C using the equation shown below (Equation 5 

in the 1999 AWQC document)

5

:

log(CVt,7,20) = log(CVt,7) - [-0.028(25°C - 20

°C)]

= 29.17 mg TAN/L

Because this is the only species in this genus for which data in appendix B are available, 

29.17 mg TAN/L is the GMCV for the genus Hyalella reported in Table 4 of this update 

document.

 

5

See footnote 4 in Appendix D.
143

Appendix F. Acute-Chronic Ratios (ACRs).

The CCC was calculated directly from chronic values (EC20s ) in Appendix B using the 

standard fifth percentile procedure provided in the 1985 Guidelines (Stephan et al. 1985). As a 

result, acute-chronic ratios (ACRs) are not necessary for the derivation of the new chronic 

criterion presented in this document. It is still worthwhile, however, for EPA to provide 

recommended ACRs for predicting chronic sensitivity of untested species using measured or 

estimated acute values for other related efforts (e.g., developing Biological Evaluations in 

support of National Endangered Species Act Consultations on EPA 304(a) criteria 

recommendations, or when an ACR(s) is allowed to derive site-specific criteria for ammonia in 

fresh water). Table F.1 below presents ACRs for all species with chronic values that were used 

in the derivation of a GMCV and for which comparable acute values were found, as well as for a 

few additional species of special interest, such as threatened and endangered species. All acute 

and chronic values were adjusted to pH 7 and to 20°C (in the case of invertebrates). For each 

species or genera where more than a single ACR was calculated, Species and Genus Mean 

Acute-Chronic Ratios (SMACRs and GMACRs, respectively) were also calculated as the 

geometric mean value of individual ACRs and SMACRs. (Note: in the case of a single ACR 

within a Genus, the ACR is the SMACR.) Additionally, taxon-specific ACRs (TSACRs) were 

calculated where practical and for purpose of comparison at the taxonomic level of Family and 

Class. 

The ACRs for freshwater aquatic invertebrates range from 2.406 to 49.45 (a factor of 21; 

see Table F.1). Likewise, the ACRs for fish range from 3.437 to 36.53 (factor of 11). The broad 

range in values can probably be explained because of the different kinds of chronic tests (lifecycle, ELS, 28-d juvenile mussel or snail) and toxicological endpoints (survival, growth, or 

reproduction) upon which they are based. The ACR of 36.53 for fathead minnow, for example, 

was based on hatchability from the life-cycle test of Thurston et al. (1986), whereas the early 

life-stage tests with fathead minnow of Mayes et al. (1986) and Swigert and Spacie (1983) gave 

ACRs of 11.35 and 17.17. The range of ACRs based on chronic values from the two early lifestage tests is small, and it is perhaps not surprising that a life-cycle test gave a higher ACR than 

the early life-stage tests. As another example illustrating the variability among ACRs from 

different kinds of tests and using different toxicological endpoints, but this time comparing 
144

amongst different species of invertebrates, the ACR of 49.45 for Lampsilis fasciola was based on 

survival from a 28-day test involving two month-old juveniles (Wang et al. 2007a,b), whereas 

the life-cycle tests with the two species of cladocerans (Ceriodaphnia acanthina and C. dubia) 

are based on adverse effects on reproduction with ACRs of 2.406 (Mount 1982) and 3.924 

(Nimmo et al. 1989), respectively (Table F.1). 

The ACRs for bivalve mollusks in general are larger compared to other freshwater 

aquatic animal taxa and range from 9.028 to 49.45. The ACRs for other freshwater invertebrates 

range from 2.406 to 15.81. The ACRs for fishes, in contrast, are quite varied even within species 

or genera. For example, the ACRs for Lepomis sp. range from 3.437 to 28.51 despite having 

been based on ELS tests and using biomass or survival as the toxicological endpoint.

Figure F.1 depicts SMACRs in relation to SMAVs to determine whether there is a trend. 

Only the weak trend of decreasing SMACR with increasing SMAV is apparent; primarily due to 

the comparatively large SMACRs for freshwater bivalve mollusks. 

In general TSACRs for most freshwater aquatic animals (excluding bivalve mollusks) are 

within the relatively small range of 5.113 to 15.81 at the Class level, and may be acceptable for 

use when certain taxon-specific chronic toxicity data are not available. Perhaps not surprisingly, 

the CCC (2.1 mg TAN/L) calculated as the quotient of the FAV of 32.99 mg TAN/L (at pH 7 

and 20°C) and geometric mean ACR for the Family Unionidae (15.52) agrees well with the CCC 

calculated directly from available chronic data (see Appendix B and Figure 4).
145

Table F.1. Species, Genus and Taxon-Specific ACRs for Freshwater Aquatic Animals Exposed to Ammonia.

Table F.1. Species, Genus and Taxon-specific ACRs for Freshwater Aquatic Animals Exposed to Ammonia

Species Scientific Name 

Acute and Chronic 

Test Endpoint pH Temp

Normalized

Values Reference ACR SMACR GMACR

TSACR

(Family)

TSACR

(Class)

Class Gastropoda (Family: Lithoglyphidae)

Fluminicola sp.

LC50 8.25 20.2 >62.15

Besser 2011 7.940 7.940 7.940 7.940 7.940

EC20 - Change in Length 8.22 20.1 7.828

Class Bivalvia (Families Unionidae and Pasidiidae)

Lampsilis fasciola

EC50 8.50 20.0 69.63 Wang et al. 2007b

49.45 49.45

21.13

15.52

25.68

EC20 - Survival 8.20 20.0 1.408 Wang et al. 2007a

Lampsilis siliquoidea

EC50 8.20 20.0 28.99 Wang et al. 2007a

9.028 9.028

EC20 - Survival 8.25 20.0 3.211 Wang et al. 2011

Villosa iris

EC50 8.40 20.0 23.29 Wang et al. 2007b

11.40 11.40 11.40 EC50 8.30 20.0 68.40 Wang et al. 2007b

EC20 - Survival 8.20 20.0 3.501 Wang et al. 2007a

Musculium transversum

EC50 8.10 14.6 109.0 West 1985; Arthur et al. 1987

42.50 42.50 42.50 42.50

EC20 - Survival 7.80 21.8 2.565 Sparks and Sandusky 1981

Class Branchiopda (Family: Daphniidae)

Ceriodaphnia acanthina

EC50 7.06 24.0 154.3

Mount 1982 2.406 2.406

3.073

5.113 5.113

EC20 - Reproduction 7.15 24.5 64.10

Ceriodaphnia dubia

EC50 7.80 25.0 152.9

Nimmo et al. 1989 3.924 3.924

EC20 - Reproduction 7.80 25.0 38.96

Daphnia magna

EC50 8.50 20.0 296.9 Gersich and Hopkins 1986

8.186

8.507 8.507

EC20 - Reproduction 8.45 19.8 36.27 Gersich et al. 1985

EC50 8.34 19.7 419.1

Reinbold and Pescitelli 1982a 8.841

EC20 - Reproduction 7.92 20.1 47.40

Class Malacostraca (Family: Dogielinotidae)

Hyalella azteca

EC50 8.30 25.0 461.2 Ankley et al. 1995

15.81 15.81 15.81 15.81 15.81

EC20 - Biomass 8.04 25.0 29.17 Borgmann 1994
146

Table F.1. Species, Genus and Taxon-specific ACRs for Freshwater Aquatic Animals Exposed to Ammonia

Species Scientific Name 

Acute and Chronic 

Test Endpoint pH Temp

Normalized

Values Reference ACR SMACR GMACR

TSACR

(Family)

TSACR

(Class)

Class Actinopterygii (Families Salmonidae, Catostomidae, Cyprinidae, Ictaluridae and Centrarchidae)

Oncorhynchus clarkii LC50 7.81 13.1 132.3 Thurston et al. 1978

5.122 5.122

5.518 5.518

8.973

O. clarkii henshawi EC20 - Survival 7.57 13.7 25.83 Koch et al. 1980

Oncorhynchus mykiss

LC50 7.40 14.5 31.47 Calamari et al. 1981

9.696

5.945

EC20 - Survival 7.40 14.5 3.246 Calamari et al. 1977, 1981

LC50 7.67 7.7 40.40 Thurston et al. 1981a

3.646

EC20 - 5 yr Life Cycle 7.70 7.5-

10.5 >11.08 Thurston et al. 1984a

Catostomus commersoni

LC50 8.16 15.0 176.6

Reinbold and Pescitelli 1982c

LC50 8.14 15.4 166.3 14.75 14.75 14.75 14.75

EC20 - Biomass 8.32 18.6 11.62 Reinbold and Pescitelli 1982a

Notropis topeka

LC50 8.09 13.2 147.3 Adelman et al. 2009

(EC20 from Appendix C) 8.437 8.437 8.437

10.96

EC20 - Growth Rate 8.07 12.4 17.45

Pimephales promelas

LC50 7.76 19.0 139.3

Thurston et al. 1983, 1986 36.53

19.24 19.24

LC50 7.83 22.0 158.7

LC50 7.91 18.9 178.9

LC50 7.94 19.1 162.3

LC50 8.06 22.0 205.0

LC50 8.03 22.1 216.3

EC20 - LC Hatchability 8.00 24.2 4.784

LC50 8.14 22.0 141.2

Mayes et al. 1986 11.35

EC20 - Survival 8.00 24.8 12.43

LC50 7.78 25.9 117.3

LC50 7.80 25.6 126.8 Swigert and Spacie 1983 17.17

EC20 - Biomass 7.82 25.1 7.101

Cyprinus carpio

LC50 7.72 28.0 133.9 Hasan and MacIntosh 1986

8.100 8.100 8.100

EC20 - Growth: Weight 7.85 23.0 16.53 Mallet and Sims 1994

Ictalurus punctatus

LC50 7.80 25.7 97.67

Swigert and Spacie 1983 4.800 4.800 4.800 4.800

EC20 - Biomass 7.76 26.9 20.35

Lepomis cyanellus

LC50 7.72 22.4 144.3

McCormick et al. 1984 12.18

EC20 - Biomass 7.90 22.0 11.85 6.468 13.58 13.59

LC50 8.28 26.2 62.07 Reinbold and Pescitelli 1982a 3.437
147

Table F.1. Species, Genus and Taxon-specific ACRs for Freshwater Aquatic Animals Exposed to Ammonia

Species Scientific Name 

Acute and Chronic 

Test Endpoint pH Temp

Normalized

Values Reference ACR SMACR GMACR

TSACR

(Family)

TSACR

(Class)

EC20 - Survival 8.16 25.4 18.06

Lepomis macrochirus

LC50 7.60 21.7 93.31

Smith et al. 1984 28.51 28.51

EC20 - Biomass 7.76 22.5 3.273

Micropterus dolomieui

LC50 (pH 6.5) 6.53 22.3 269.2

Broderius et al. 1985

31.12

13.61 13.61

EC20 (pH 6.5) - Biomass 6.60 22.3 8.650

LC50 (pH 7.0) 7.16 22.3 144.3

14.84

EC20 (pH 7.0) - Biomass 7.25 22.3 9.726

LC50 (pH 7.5) 7.74 22.3 105.2

6.670

EC20 (pH 7.5) - Biomass 7.83 22.3 15.77

LC50 (pH 8.5) 8.71 22.3 126.0

11.14

EC20 (pH 8.5) - Biomass 8.68 22.3 11.31
148

Figure F.1. SMACRs by SMAV Rank.

1

1 0

100

0.0 50.0 100.0 150.0 200.0 250.0

SMACR (from Table F.1)

Species Mean Acute Value 

(from Table 3)

Relationship Between SMACR and SMAV

Freshwater

Freshwater Unionid Mussels

Other Freshwater Mollusks - Snail

Other Freshwater Invertebrates

Freshwater Fish

Other Freshwater Mollusks - Bivalve
149

Appendix G. Results of the Regression Analyses of New Chronic Data for Unionid 

Mussels.

This appendix provides the figures generated using EPA’s TRAP program that was used

to calculate EC20s for the new chronic ammonia toxicity studies conducted with unionid mussels. 

In the figures that follow, circles denote measured responses and solid lines denote estimated

regression lines. The model-estimated EC20 values and corresponding 95% confidence limits are 

provided with each figure, as well as the pH and water temperature at which the test was 

conducted. Per the text on page 32 in Chronic Toxicity to Freshwater Aquatic Animals and as 

discussed in greater detail on page 56 in Effects Characterization, EPA decided that while 28-

day survival EC20s from these tests using juvenile freshwater mussels are acceptable for 

derivation of a chronic aquatic life criterion for ammonia, EC20s based on growth responses from 

these tests are not. The decision not to use the growth data from these tests was based on the 

uncertainty in the test methods for assessing the growth endpoint and the need for additional 

research “to optimize feeding conditions, to conduct longer-term exposures (e.g., 90 d), and to 

compare growth effect to potential reproductive effect in partial life-cycle exposure” (Wang et al. 

2011). Additionally, the growth response during these tests show a high degree of variability, 

and the test methods for assessing growth, based on substrate or water-only exposures, are 

currently being evaluated – see Figure below depicting the growth response of juvenile 

fatmucket in the 28-day tests reported in Wang et al. (2011).
150 Juvenile Fatmucket, 28-Day Survival, Wang et al. 2011

log (Total Ammonia - mg TAN/L)

-1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4

Survival at 28 Days (%)

0

20

40

60

80

100

EC20 = 0.8988 mg TAN/L (95% CI = 0.7142-1.131)

T = 20°C

pH = 8.25
151 Juvenile Wavy-rayed Lampmussel, 28-Day Survival, Wang et al. 2007a

log (Total Ammonia - mg TAN/L)

-1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4

Survival at 28 Days (%)

0

20

40

60

80

100

EC20 = 0.4272 mg TAN/L (95% CI = 0.2321-0.7861)

T = 20°C

pH = 8.2
152 Juvenile Rainbow Mussel, 28-Day Survival, Wang et al. 2007a

log (Total Ammonia - mg TAN/L)

-1.5 -1.0 -0.5 0.0 0.5 1.0

Survival at 28 Days (%)

0

20

40

60

80

100

EC20 = 1.063 mg TAN/L (95% CI = 0.9814-1.150)

T = 20°C

pH = 8.2
153 Juvenile Fatmucket, 28-Day Growth, Wang et al. 2011

log (Total Ammonia - mg TAN/L)

-1.4 -1.2 -1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4

Dry Weight at 28 Days (mg)

0.00

0.04

0.08

0.12

0.16

0.20

An EC20 cannot be calculated for these data. 

T = 20°C

pH = 8.25
154

Appendix H. Detailed Descriptions of Select New Acute and Chronic Toxicity Test Data 

Used for Criteria Derivation.

Acute Toxicity Test Data

Venustaconcha ellipsiformis (ellipse)

As noted above, the ellipse test data was not directly used in the acute criterion 

calculation, but the data is described here as additional evidence supporting the determined acute 

criterion value. The GMAV for the ellipse is based on the 24-hr EC50 reported for an acute 

toxicity test initiated with 2-hr old glochidia of the species (Wang et al. 2007b). Glochidia were 

tested under static conditions at pH 8.1 and 20°C. Survival of control animals after 24 hours was 

90 percent. The estimated measured EC50 at test temperature and pH was 4.450 mg N/L, after 

adjusting the reported nominal EC50 by multiplying by a factor of 0.89 (i.e., measured total 

ammonia concentrations were 89 percent of nominal concentrations for 24 hour glochidia 

exposures). The GMAV for this species is 23.12 mg TAN/L when adjusted to pH 7 and 20°C

(Appendix A), and represents the lowest in the acute dataset (Table 3). The acute criterion of 17 

mg TAN/L is considered protective of this species because the GMAV/2, a value used to 

estimate an effect level un-differentiable from controls (Federal Register on May 18, 1978 (43 

FR 21506-18), is approximately 12 mg TAN/L for the ellipse, which is close to the current 

criterion value, given the variability and uncertainty in such toxicity tests. 

Utterbackia imbecillis (pondshell mussel)

The GMAV for pondshell mussel of 46.93 mg TAN/L is the sixth lowest in the acute 

dataset (Table 3). Although this GMAV is not one of the four used in calculating the FAV, the 

value is composed of individual EC50 values ranging from a comparatively low acute value of 

17.91 to 100.5 mg TAN/L (expressed as TAN and normalized to pH 7 and 20°C, Appendix A). 

This GMAV is based on several EC50s (numbering nine in total) from three different studies 

(Wade et al. 1992; Keller 2000; Black 2001). This particular GMAV is based on tests with 

predominantly juvenile mussels of various ages, but also including a single test which employed 

glochidia (Appendix A). The pH and test temperature for all nine tests was relatively uniform 

and ranged from 7.80 to 8.35 and 24.0 to 25.1°C, respectively. Control survival exceeded 90 

percent in all tests regardless of life-stage tested. 
155

Fusconaia masoni (Atlantic pigtoe)

The GMAV for the Atlantic pigtoe represents the seventh lowest in the acute dataset, and 

lies just below the lowest GMAV for the most sensitive fish species, the mountain whitefish 

(Table 3). This GMAV is based on the 6-hr EC50 reported for an acute toxicity test initiated with 

2-hr old glochidia of the species (Black 2001). Glochidia were tested under static conditions at 

pH 7.6 and 24.9°C. Survival of control animals after 6 hours was 93 percent, falling to 87 

percent after 12 hours. The EC50 at test temperature and pH was 15.90 mg TAN/L, or 47.40 mg 

TAN/L when adjusted to pH 7 and 20°C (Appendix A). 

Fluminicola sp. (pebblesnail) 

The GMAV of 62.15 mg TAN/L for Fluminicola is the tenth most sensitive in the acute 

dataset (Table 3). As part of the study to evaluate the chronic sensitivity of pebblesnails 

(Gastropoda: Hydrobiidae) to ammonia via 28-day water only toxicity tests (see additional 

details below under Chronic Toxicity Test Data: 28-day Tests with Juvenile and Adult 

Pebblesnails (Fluminicola species), Besser (2011) reported survival of ‘large’ snails (i.e., mean 

starting shell length of 1.81 mm) after 96 hours of exposure. No mortality was observed in 

controls through the highest test concentration of 8.801 mg TAN/L where 32 of 40 snails (80 

percent) survived. The mean pH and test temperature at this highest ammonia treatment level 

were 8.25 and 20.2°C, respectively. Because only 20 percent mortality occurred at this test 

concentration, the EC50 at test temperature and pH is recorded in this document as > 8.801 mg 

TAN/L, or >62.15 mg TAN/L when adjusted to pH 7 and 20°C (Appendix A).

Pleurocera uncialis (pagoda hornsnail)

Another non-pulmonate snail species (pagoda hornsnail) was determined to be nearly as 

sensitive to ammonia as pebblesnail, the pagoda hornsnail, which was ranked 12th in acute 

sensitivity. Goudreau et al. (1993) collected and acclimated (for six days) adult snails from 

Clinch River, Virginia prior to conducting a static renewal bioassay to determine a 96-hr LC50

for this species. The test was conducted in a walk-in experimental chamber set to a temperature 

of 22°C and using chlorine free laboratory dilution water at pH 8.1. Survival of adult snails in 

the control treatment was 100 percent. The reported LC50 at test temperature and pH was 11.18 
156

mg TAN/L when expressed as total ammonia. The LC50 normalized to pH=7 and 20°C is 68.54 

mg TAN/L (Appendix A). 

Deltistes luxatis (Lost River sucker)

The endangered Lost River sucker is a freshwater fish species endemic to the Klamath 

Basin of northern California and southern Oregon (Appendix A). The acute toxicity of ammonia 

was determined for larval and juvenile Lost River sucker as reported in Saiki et al. (1999). 

Larval tests were initiated when fish reared from spawned eggs were 35 days old, whereas the 

juvenile tests were initiated after the fish reached 3-7 months old. All fish were exposed for 96 

hours under flow-through conditions at pH 8.0 and 20°C. The reported LC50s at test temperature 

and pH were 10.35 and 16.81 mg/L for larval and juvenile fish, expressed as total ammonia 

nitrogen (Appendix A). The LC50s normalized to pH 7 and 20°C are 44.42 and 72.18 mg 

TAN/L, respectively (Appendix A). The GMAV for Lost River sucker is calculated as the 

geometric mean of the two normalized LC50s, or 56.62 mg TAN/L (Table 3). Lost River sucker 

represents the ninth most sensitive genus in the acute dataset, and second most sensitive fish 

species (following mountain whitefish which was the most sensitive GMAV) and is expected to

be protected by the CMC of 17 mg TAN/L.

Chronic Toxicity Test Data

28-day Tests with Juvenile and Adult Pebblesnails (Fluminicola species)

The summary for 28-day tests recently conducted with Fluminicola sp. includes the 

results from repeat tests performed by Besser et al. in 2009 and 2010, the details of the latter of 

which are summarized in a memorandum to EPA in 2011 (this study referred to in this document 

as Besser 2011). 

Test organisms used in the Besser et al. (2009) 28-day survival tests with wild-caught 

(Snake River, Idaho) Fluminicola sp. included mixed-aged adult and young-adult organisms 

(from 6 to 12 months). Mixed-age classes were used because the acclimation cultures produced 

only approximately 200 neonates for testing that were collected over a period of about four 

months. Despite the fact that snails in the control treatment exhibited 100 percent survival, while 

snails exposed to the highest ammonia concentration (7.9 mg TAN/L) exhibited 0 percent 

survival, extreme variation between replicates at the highest test concentrations was observed 
157

during the test, i.e., snails in replicates were either all alive or all dead in the 1.7 and 3.6 mg 

TAN/L treatments. Based on the mean survivals for Fluminicola sp., the reported survival EC20

for the species was estimated to be 1.02 mg TAN/L at test temperature (20.8°C) and pH (8.26), 

or 3.900 mg TAN/L when adjusted to pH 7 and 20°C (see Appendix C). The EC20 reported for 

the test is not considered reliable, however, due to the variability in survival among replicates in 

the 1.7 and 3.6 mg TAN/L test concentrations; therefore, this data was not used in the derivation 

of the final ammonia CCC (i.e., the all-or-none response in the replicates of these two treatments, 

which, when averaged and used as means instead of analyzing the replicates separately in the 

regression, allows estimation of an EC20 that would otherwise be incalculable because of the 

variability between treatment replicates). Thus, the upper limit CV for the test is uncertain. The 

value clearly is a concentration below 7.9 mg TAN/L (at test temperature and pH), but the exact 

concentration could not be determined at the time.

In an attempt to further define the 28-day ammonia survival effects threshold for 

Fluminicola sp., pebblesnails cultured in the laboratory at the USGS Columbia Environmental 

Research Center were tested in April 2010 via a similar 28-day test protocol (see Besser 2011). 

This 2010 test was conducted with two size classes of juvenile pebblesnails: small (mean shell 

length of 1.34 mm at the start of the test) and large (mean starting shell length of 1.81 mm). 

Both size groups were exposed in the same flow-through exposure system consisting of five 

ammonia concentrations (ranging from a nominal concentration of 0.5 to 8 mg N/L in 50 percent 

dilution series), plus a control, with four replicates of ten snails per replicate (or 40 small and 40 

large snails per treatment). Mean measured TAN concentrations, pH, and temperature were 

maintained very close to target values throughout the test (i.e., mean measured ammonia 

concentrations were within 14 percent of nominal, mean treatment pH ranged from 8.18 to 8.26, 

and mean treatment water temperature ranged from 20.1 to 20.2°C). Survival was measured 

after 4 and 28 days. Survival of snails after 28 days in the small size group was lower overall 

(75 percent in the control and 60-68 percent in the nominal 0.5 to 2 mg TAN/L test concentration 

range) in relation to that of the large size group (93-100 percent in both the control and low 

ammonia test concentration). For both size groups, snail survival differed among test 

concentrations and was substantially lower than controls in the two highest ammonia 

concentrations (4.0 and 8.0 mg TAN/L nominal), however, due to the lower control survival of 

the small size group (<80 percent), the data for this group is not used quantitatively in the 
158

derivation of the final ammonia CCC and is instead presented in Appendix C as other chronic 

data.

Because the survival of the large size group of snails was acceptable in controls and snail 

length different among concentrations according to concentration-response, change in length for 

the large size group was analyzed further for inclusion in the derivation of the CCC. (Note: 

attempts to model concentration-response curves for survival in the large size group using TRAP 

software were not as informative because partial mortality was limited to only one treatment 

(i.e., 28-day survival ranged from 98 to 100 percent in the nominal 0.5, 1 and 2 mg TAN/L test 

concentrations, only 10 percent in the 4 mg TAN/L nominal test concentration, and zero percent 

at the highest nominal test concentration of 8 mg TAN/L). The growth EC20 for this freshwater 

non-pulmonate snail species calculated using EPA’s TRAP (threshold sigmoid model with full 

convergence) is 2.281 mg TAN/L at test pH (8.22) and temperature (20.1°C), or; 7.828 mg 

TAN/L after adjustment to pH 7 and 20°C (see Appendix B). The TRAP output for this test is 

provided below to support the use of the growth-based EC20 for this particular species and test. 
159

Chronic Toxicity Tests with Juvenile Hyalella azteca 

Borgmann (1994) conducted four sets of experiments on H. azteca using different 

dilution water types and life-stages of test organisms. One set of experiments consisted of tests 

that began with <1-week-old organisms, all of which utilized weekly renewals and dechlorinated 

tap water originating from Lake Ontario. Of the three tests, one lasted four weeks and the other 

two lasted 10 weeks, the latter of which produced data on both survival and reproduction, as 

described in detail in the 1999 AWQC document (U.S. EPA 1999). At the time, the results of 

the two 10-week tests were deemed sufficiently similar such that the results were analyzed 

together and subsequently used as the basis for the pH and temperature adjusted EC20 of <1.45 

mg TAN/L (at pH 8 and temperature 25°C ) reported in Table 5 of the 1999 AWQC document 

(U.S. EPA 1999). Since then, however, EPA has re-evaluated the results of the three tests in 

light of the recent extensive research that has been undertaken to elucidate the specific water 

Large Pebblesnail, 28-Day Growth, Besser et al. 2011

log (Total Ammonia - mg TAN/L)

-1.0 -0.8 -0.6 -0.4 -0.2 0.0 0.2 0.4 0.6 0.8

log(Change in Length after 28 Days - mm)-1.0

-0.8

-0.6

-0.4

-0.2

EC20 = 2.281 mg TAN/L (95% CI = 1.116-4.665)

T = 20.1°C

pH = 8.22
160

ionic composition and feeding requirements necessary to ensure the health of this particular 

freshwater aquatic test organism for use in long-term toxicity testing. During the EPA’s reevaluation of these tests, it was concluded that while the ionic composition of the water used for 

testing (dechlorinated city tap water originating from Lake Ontario) was acceptable, the results 

of the two 10-week chronic tests should not be used for deriving AWQC for the following 

reasons:

 Low control survival observed after 10 weeks of exposure (only 66.3%), possibly linked 

to inadequate food and feeding level that was employed, particularly after the first four 

weeks of testing;

 Poor control reproduction observed after 10 weeks of exposure; and 

 The fact that the ammonia concentrations increased substantially in critical test 

treatments (e.g., the 0.1 mM ammonia treatment) during the final 3 weeks of testing 

(weeks 7 – 10).

However, four week data for these two tests, in combination with data from the third 

four-week test with the same life stage, were not affected by these limitations. The measured 

total ammonia concentrations and mean pH (8.04) reported for the “Tap water (young)” tests in 

Table 1 of Borgmann (1994) reflect the analytical measurements combined from all three tests 

conducted with this life stage (i.e., <1 wk old H. azteca). Likewise, the pooled results for 

survival (from Figure 1a) and wet weight (from Table 4) reflect the observations (weekly for 

survival and after four weeks for wet weight) from the three respective tests, and thus, represent 

observations stemming from six test replicates per treatment when combined. Using these data 

up through the first four weeks of exposure, as well as the water temperature of 25°C 

(maintained via an incubator) at which all sets of experiments in the study were run, a 28-day 

EC20 of 29.17 mg N/L (based on biomass and normalized to pH 7 and 20°C) was calculated for 

H. azteca for the study (Appendix B). These data were deemed sufficient to derive an SMCV for 

the species (as an upper limit), which is subsequently used here for chronic criterion 

development. This decision was largely predicated on the fact that:

 The ion composition of the water used in this test was acceptable;

 The control survival for the tests up through the first four weeks was good (88.4%); and
161

 The feeding level during the first four weeks of testing was acceptable (as judged via the 

growth performance of the test organisms during this timeframe.

New Chronic Data for Non-salmonid Fish Species

Cyprinus carpio (common carp)

Mallet and Sims (1994) conducted a 28-day early life-stage test starting with eggs 

approximately 6 hours post-fertilization. Mean pH and temperature for the test were 7.85 and 

23°C, respectively. The measured DO concentrations reported for the test ranged from 79 to 94 

percent of saturation. Ammonia had no effect on hatching success at the highest concentration 

tested (19.6 mg TAN/L); although survival of the post-hatch stages was significantly reduced at 

this level compared to controls (average fry survival in the control treatment was 86 percent). 

Growth of fry was the most sensitive endpoint, and mean fry wet weights were inhibited at 

concentrations ≥10.4 mg TAN/L. Even though the number of larvae in each replicate vessel was 

not made uniform on hatching, at least one vessel per concentration contained an equivalent 

stocking density (23 to 29 carp), so the mean wet weight of carp in the one selected replicate per 

concentration was analyzed using regression analysis. The resulting EC20 value was 8.360 mg 

TAN/L at 23°C and pH 7.85, which is calculated to be 16.53 mg TAN/L at pH 7, with a GMCV 

sensitivity rank of ten (see Appendix B and Table 4). 

Esox lucius (northern pike)

Harrahy et al. (2004) conducted a 52-day early life-stage test starting with newlyfertilized northern pike embryos. The mean dissolved oxygen concentration in test water ranged 

from 8.7 to 9.1 mg/L during the test. There was no effect of ammonia on hatching success up to 

62.7 mg TAN/L, and larval survival of control fish was 100 percent. A significant reduction in 

larval survival and growth was observed at concentrations of total ammonia ≥30.4 and 15.1 mg 

TAN/L, respectively, at pH 7.62 and 8.7°C. The estimated EC20 value reported for biomass was 

13.44 mg TAN/L, which, normalized to pH 7 to support criteria development in this document,

is 20.38 mg TAN/L (Appendix B). The GMCV of 20.38 mg TAN/L for northern pike is 

included in Table 4 as the GMCV ranked 11th in sensitivity.
162

New Chronic Toxicity Data for Salmonid Species

Chronic values for two additional studies with Oncorhynchus species are included in this 

AWQC document. Koch et al. (1980) exposed Lahontan cutthroat trout (Oncorhynchus clarkii

henshawi) for 103 days in an ELS test. The measured dissolved oxygen concentrations for the 

entire study ranged from 7.0 to 8.9 mg/L, with an overall average of 7.9 mg/L. Survival of 

embryos in the control treatment was 80 percent, with approximately 95 percent surviving 

through the fry stage, and 80 percent surviving as fingerlings up to day 94 of the test. There 

were no successful hatches at exposure levels of 148 mg TAN/L or higher and no significant 

mortality at exposure levels below 32.9 mg TAN/L. Regression analysis of the survival data 

using an arcsine transformation resulted in a calculated EC20 value of 17.89 mg TAN/L at 13.7°C 

and pH 7.57. The EC20 value is 25.83 mg N/L when adjusted to pH 7 (Appendix B).

The recent results of a 90-day ELS test using a wild strain of rainbow trout exposed to 

ammonia were reported by Brinkman et al. (2009). The test was initiated with newly fertilized 

embryos (<24 h) exposed under flow-through conditions through hatch (28 days), swim-up (15 

days) and early fry development (52 days) to five concentrations of total ammonia with a control. 

Each treatment consisted for four replicates containing 20 embryos each (N = 100 embryos per 

treatment). Mean pH and temperature of test water measured among treatments was 7.75 and 

11.4°C, respectively. Hatch success and survival of sac fry were similar to controls for all 

ammonia concentrations, resulting in an unadjusted NOEC of >16.8 mg TAN/L. Survival, 

growth and biomass of swim-up fry were significantly reduced at 16.8 mg TAN/L compared to 

controls, but unaffected at 7.44 mg N/L, resulting in a chronic value (MATC) of 11.2 mg 

TAN/L. The EC20 calculated for biomass using TRAP and normalized to pH 7 is 15.60 mg 

TAN/L (Appendix B).
163

Appendix I. Qualitative Weight-of-Evidence Test Data.

Additional 28-day Toxicity Test data for Freshwater Mussels

As part of the same study summarized above in the Effects Analyses to Freshwater 

Aquatic Organisms under Summaries of Studies Used in Chronic Criterion Determination (page 

34), Wang et al. (2007a) also attempted to determine the effect of ammonia on growth of 2-

month old juvenile rainbow mussel, fatmucket, and wavy-rayed lampmussel. The 28-day tests

were conducted following the same methods (see ASTM 2006). The mean length of juvenile 

rainbow mussel and fatmucket exposed to the lowest ammonia concentrations tested was reduced 

by 13 and 12 percent compared to mean length of control animals, respectively, but increased by 

7 percent for the wavy-rayed lampmussel. There was no consistent effect of ammonia, however, 

on either length at 28 days or change in length after 28 days for fatmucket and wavy-rayed 

lampmussel at test concentrations where survival was unaffected; only the 28-day test with 

rainbow mussel exhibited such a concentration- response for length and change in length. For 

the reasons explained above under the section referenced, the growth endpoint was not used from 

these tests to derive the chronic criterion, and instead, the reported IC25 (inhibition concentration) 

estimated for these tests are included in Appendix C. The reported growth IC25 for juvenile 

rainbow mussel, fatmucket, and wavy-rayed lampmussel from their respective 28-day tests were 

0.73, 0.44, and 0.57 mg TAN/L at test pH of 8.2 and temperature 20°C. These values, when 

adjusted to pH 7 and 20°C, are 2.406, 1.450 and 1.878 mg TAN/L, respectively (see Appendix 

C).

Additional 28-day Toxicity test Data for Freshwater Snails

Besser et al. (2009), in a USGS study report completed for EPA, conducted 28-day flowthrough survival and growth tests with five species of snails, including four gill-bearing (nonpulmonate) species and an air-breathing (pulmonate) species. All tests were conducted in ASTM 

hard water (mean hardness and alkalinity of approximately 170 and 120 mg/L as CaCO3, 

respectively) with a pH range of 8.20-8.29 and a temperature range of 19-21°C during testing. 

Total ammonia nitrogen (mg TAN/L) concentrations in tests were measured weekly with the 

percent of nominal concentrations ranging from 83 to 101 percent. Test results were based upon 
164

the mean of the measured concentrations. For all snail exposures, the effect of ammonia on 

growth was not determined for test species that were of mixed ages at test initiation (as explained 

further below); growth, however, was not as sensitive of an endpoint as survival for at least one 

(Pyrgulopsis idahoensis) of the two snail species (Lymnaea stagnalis and P. idahoensis) where 

both growth and survival were measured (see Appendix C).

Fontigens aldrichi (Ozark springsnail)

As part of the original study described above, Besser et al. (2009) also determined the 

effect of ammonia on survival of the non-pulmonate snail F. aldrichi. Because F. aldrichi did 

not reproduce during culturing and acclimation, field-collected organisms of “older” (adult) 

mixed-ages were used for ammonia exposures. F. aldrichi exposed to ammonia in the 28-day 

test exhibited approximately 94 percent survival at 0.45 mg TAN/L, but only 50 percent at 0.83 

mg TAN/L. Similar to the 2009 adult pebblesnail study, the replicates associated with the latter 

0.83 mg TAN/L treatment in particular were characterized by high variability, and therefore,

these data were not used quantitatively in the derivation of the final ammonia CCC. In addition, 

field-collected F. aldrichi did not reproduce in captivity and animals in the control group did not 

grow during testing. The reported EC20 for F. aldrichi was 0.61 mg TAN/L, or 2.332 mg TAN/L 

when adjusted to pH 7.0 and 20°C, and is presented as other chronic data in Appendix C.

Pyrgulopsis idahoensis (Idaho springsnail)

Two separate 28-day tests with the de-listed (from the Federal threatened and endangered 

species list) non-pulmonate snail species, P. idahoensis, were conducted which included 

exposing juvenile organisms that were 7-9 and 11-13 weeks post-hatch (organisms in each 

cohort tested as separate replicates in the same test; test identified as test #3 in the 2009 Besser et 

al. report), as well as a cohort of mixed-age adults for all subsequent tests (test identified as test 

#5 in Besser et al. 2009). The older life stages were chosen for testing because of the high 

control mortality demonstrated in preliminary tests using 2-3 week post-hatch P. idahoensis. 

In the 28-day test with juveniles, snails in four of the five test concentrations exhibited 

≤44.4 percent survival, whereas control survival was 100 percent; the single exception being the

snails in the middle test concentration of 1.8 mg TAN/L, which demonstrated only 62.5 percent 

survival. The survival EC20 reported for the test was 0.48 mg TAN/L at 20.1°C and pH 8.25, or 
165

1.726 mg TAN/L when adjusted to pH 7 and 20°C, however, due to the poor concentrationresponse relationship exhibited in this test, this EC20 is highly uncertain, and therefore, the data 

are included in Appendix C as “other data” and are not used in the derivation of the CCC. 

The 28-day chronic test initiated with mixed-aged adult P. idahoensis (4 to 8 months of 

age), on the other hand, resulted in an EC20 reported for the test of 3.24 mg TAN/L, or 12.39 mg 

TAN/L when adjusted to pH 7 and 20°C (Appendix C). Comparison of the juvenile and adult P. 

idahoensis survival results indicates that juveniles are possibly the more sensitive of the two life 

stages; however, due to the unreliability of the juvenile data, specifically the irregular survival 

concentration-response relationship, such an assertion is uncertain at this time and the CVs are 

not used quantitatively in the derivation of the CCC.

Taylorconcha serpenticola (Bliss Rapids snail)

A non-pulmonate snail species listed under the Endangered Species Act, Taylorconcha 

serpenticola, was exposed to ammonia in 28-day flow-through toxicity tests as described above. 

Because T. serpenticola did not reproduce or grow well during culturing and acclimation, fieldcollected organisms of “older” (adult) mixed-ages were used. Survival of snails in the control 

treatment was 100 percent, whereas survival of snails exposed to concentrations up to 3.6 mg 

TAN/L exceeded 80 percent. Survival of snails exposed to the highest concentration tested (7.9 

mg TAN/L) was reduced to only 30 percent. The survival EC20 reported for T. serpenticola in 

the test was 3.42 mg TAN/L at 20.8°C and pH 8.26, or 13.08 mg TAN/L at pH 7.0 and 20°C, but 

because these snails did not grow well preceding the test, the data are also considered “other 

data” and placed in Appendix C. 

Pleurocera canaliculata (silty hornsnail)

EPA sponsored a study (GLEC 2011) to independently confirm the results of the 28-day 

juvenile and adult tests performed by the USGS, Columbia, MO laboratory (i.e., Besser et al. 

2009 and Besser 2011) with non-pulmonate snails. The USGS test results indicated that 

specialized and Federally-listed non-pulmonate gill-bearing snails, such as the Idaho springsnail, 

Bliss Rapids snail and pebblesnail, are potentially: 1) sensitive to prolonged, 28-day ammonia 

exposure, and 2) as sensitive as ammonia-sensitive freshwater unionid mussel species to such 

exposure. The EPA-sponsored study involved a 28-day flow-through toxicity test using a more 
166

widely-distributed non-pulmonate snail species, P. canaliculata. Two other non-pulmonate snail 

species were also selected based on distribution and generalized habitat preference; however, P. 

canaliculata was the only one of the three wild-caught snail species that were successfully held 

and maintained in the laboratory for subsequent testing. Following a protocol similar to that 

used in the USGS studies, a 28-day toxicity test of mature, mixed-age P. canaliculata was 

conducted. The test design consisted of five ammonia test concentrations (0.9, 1.9, 3.8, 7.5, and 

15 mg TAN/L, nominal) and one control, with four replicate chambers containing six snails each 

per test concentration (N=24 snails per treatment). Test concentrations were based on the results 

of a 96-hr range finding test with the species, which provided a 96-hr EC50 of 9.66 mg TAN/L, 

or approximately 88 mg N/L at 20°C and pH 7.0. The endpoint for the 28-day toxicity test was 

mortality or immobilization, measured daily, the results of which were used to calculate an EC20

(at pH 7 and 20°C) of 1.845 mg TAN/L (Appendix C). However, due to the high degree of 

temporal variability in the measured total ammonia concentrations, as well as the unequal 

response amongst replicates at the 1.9 mg TAN/L nominal test concentration, these data were not 

used quantitatively in the derivation of the final ammonia CCC; a 28-day ammonia survival 

effect concentration of <7.667 mg TAN/L was recommended as the CV for the species which 

supports the recent findings for the pebblesnails (1.8 mm) which were re-tested and reported to 

EPA via Besser (2011).

(Note: The calculated EC20 values using TRAP for P. idahoensis, F. aldrichi, and T. 

serptenticola, and the recommended 28-day ammonia survival effects concentration of <7.667

mg TAN/L for P. canaliculata, are deemed representative of non-pulmonate snail sensitivity in 

general and are included in Appendix C for the purpose of comparison.) 

Lymnaea stagnalis (pulmonate pondsnail)

The effect of ammonia in a 28-day test on survival and growth of a third freshwater snail 

species, the air-breathing L. stagnalis, was also reported in Besser et al. (2009). The tests with L. 

stagnalis utilized organisms that were <1 week post-hatch due to the abundance of young 

produced during culturing. L. stagnalis exposed to ammonia in a 28-day flow-through test 

exhibited approximately 98 percent survival at the highest concentration tested (8.0 mg TAN/L). 

Because of the apparent negligible effect of ammonia on growth (i.e., the magnitude of the 
167

growth reduction was so small, 6 percent at 1.8 mg TAN/L and only 16 percent at 8 mg TAN/L), 

only the CV of >8.0 mg TAN/L (for survival and growth) is reported in this document for the 

test, or >28.76 mg TAN/L when adjusted to pH 7 and 20°C. Note: For the purposes of this 

document, the CV for this test species is included in Appendix C and was not used in the 

derivation of the CCC because of the uncertainty of this value (> 28.76 mg TAN/L) as an upper 

limit SMCV for the species. 

Chronic Toxicity Data for Other Salmonids

A few other chronic toxicity tests produced applicable data for salmonid species that 

were excluded from Appendix B and subsequent SMCV and GMCV calculation because either 

the exposure did not include the appropriate life stage for the species, or the tests did not meet 

other general 1985 Guidelines requirements for use in calculating the CCC. These tests are 

summarized below and shown in Appendix C.

The effects of water temperature and ammonia on the swimming characteristics of brook 

charr (Salvelinus fontinalis) were investigated by Tudorache et al. (2010). Juvenile brook charr 

were exposed to four ammonia concentrations in de-chlorinated tap water for 96 hours at pH 

9.10 and 15°C. The following swimming characteristics were measured in a 4.5 m long raceway 

following this exposure: gait transition speed, maximum swimming speed, tail-beat amplitude, 

tail-beat frequency, maximum acceleration of bursts, number of bursts, distance of bursts, and 

total swimming distance. The most sensitive swimming parameters (maximum swimming speed 

and maximum acceleration) had a reported LOEC of 0.7765 mg TAN/L, or 10.86 mg TAN/L 

when normalized to pH 7.

The effects of long-term exposure of ammonia on the molecular response of Atlantic 

salmon (Salmo salar) parr were investigated by Kolarevic et al. (2012). The juvenile fish were 

exposed for 105 days to three concentrations of total ammonia nitrogen (TAN) in a flow-through 

apparatus with two different feeding regimes: full and restricted. Average water temperature 

during the exposure was 12.1°C with a pH of 6.84. There was no effect of ammonia exposure on 

survival, resulting in a NOEC of 32.29 mg N/L (highest concentration tested) in the full feeding 

regime. When normalized to pH 7, the CV for this test is >30.64 mg TAN/L.

Beamish and Tandler (1990) exposed juvenile lake trout (Salvelinus namaycush) for 60 

days on two different diets and observed a significant reduction in rate of weight gain when total 
168

ammonia was 6.44 mg TAN/L at pH 8.02 and temperature was 11.6°C. Food intake by fish was 

initially decreased at this concentration of total ammonia, but was no different from controls by 

the end of the test. The growth LOEC for the study, when adjusted to pH 7, was calculated to be 

16.10 mg TAN/L. Note: this test was not included in the calculation of the CCC because it was 

not a true ELS having been initiated with juvenile fish. 

Chronic Toxicity Data for Threatened and Endangered Fish Species

Meyer and Hansen (2002) conducted a 30-day toxicity test with late-stage larvae (0.059 

g) of Lost River suckers (Deltistes luxatus) at pH 9.43. The exposure duration and pH were 

chosen to represent the period of combined elevated unionized ammonia concentrations and 

elevated pH that occur during cyanobacterial blooms in surface waters of Upper Klamath Lake, 

which have been shown to last for several weeks to a month. Survival decreased significantly at 

1.23 and 2.27 mg TAN/L, whereas the highest NOEC for all endpoints (survival, growth, body 

ions, and swimming performance) was 0.64 mg TAN/L. Most deaths in the 2.27 mg TAN/L 

exposure occurred during the first three days of the test, while mortality of larvae in the 1.230

mg TAN/L treatment occurred gradually from days 2 to 24. The 29 percent average mortality in 

the 0.64 mg TAN/L treatment was all due to an unexplained complete loss of one replicate 

between days 5 and 7 of the exposure. Control survival was > 90 percent. The calculated LOEC 

of 1.230 mg TAN/L total ammonia normalized to pH 7 corresponds to a value of 25.31 mg 

TAN/L, substantially higher than the 2013 chronic criterion value (Appendix C).

Fairchild et al. (2005) conducted 28-day toxicity tests with early life stages of Colorado 

pikeminnow (Ptychocheilus lucius) and razorback sucker (Xyrauchen texanus), and compared 

the results of those tests with a test using a surrogate fish species, the fathead minnow 

(Pimephales promelas). Tests were initiated 2 days after swim-up when the larvae were feeding 

exogenously (or at 8-day post hatch for Colorado pikeminnow, 9-day post hatch for razorback 

sucker, and 4-day post-hatch for fathead minnow). Temperature, pH and dissolved oxygen over 

the 28-day test period averaged 19.9°C, 8.24, and 7.4 mg/L (80 percent saturation) over the 

course of the three studies. Control mortality was 7 percent (fathead minnows and Colorado 

pikeminnow) or less (3 percent, razorback sucker) on day 28. Effect concentrations based on the 

survival and growth endpoints of the fathead minnow and razorback sucker tests were not 

different; however, growth was the more sensitive endpoint for the Colorado pikeminnow test. 
169

The 28-day growth LOEC for the Colorado pikeminnow was 8.60 mg N/L, or 29.75 mg TAN/L 

at pH 7, substantially greater than the 2013 chronic criterion. The 28-day survival LOEC for the 

razorback sucker was 13.25 mg TAN/L, or 46.58 mg TAN/L at pH 7. Both endangered fish 

species exhibited similar sensitivity to ammonia as the fathead minnow (LOEC of 32.71 mg 

TAN/L at pH=7; see Appendix C). The same can be said for the Lost River sucker, which 

indicates that these particular endangered fish species will be protected by the CCC value 

calculated in this 2013 AWQC Update.

Finally, Adelman et al. (2009) conducted both acute and chronic toxicity tests with 

ammonia on the endangered Topeka shiner (Notropis topeka) and compared those values to 

chronic studies with fathead minnows. All tests used a flow-through dosing apparatus and deep 

well water with a total hardness and alkalinity of 210-230 mg/L CaCO3, and chloride 

concentration of 0.64-1.04 mg/L. Acute survival studies with Topeka shiner lasted 96 hours and 

were conducted on two different life-stages (juvenile and adult) and at two test temperatures, 

warm, 25°C (adult and juvenile), and cold, 13°C (juvenile only). LC50s for total ammonia 

ranged from 18.7-21.4 mg TAN/L at 25°C and 28.9 mg TAN/L at 13°C; all acute studies were 

conducted at approximately pH 8. Normalized to pH 7, the 96-hr LC50s were 69.59 – 88.27 mg 

TAN/L at 25°C and 147.3 mg TAN/L at 13°C, both substantially greater than the acute criterion 

value of 17 mg TAN/L, respectively (see Appendix A).

Chronic studies with Topeka shiners started with both adults and juveniles, since 

embryos were not available, and lasted 30 days. The results of the survival and growth studies 

with juvenile Topeka shiners were compared to a 30-day juvenile survival study and 32-day 

embryo-larval study conducted with fathead minnows in the same dilution water. The authors 

interpreted the results of the relationship between the comparative studies using Topeka shiners 

versus fathead minnows to infer what an expected result for an embryo-larval study with Topeka 

shiner would be. Reported MATC values (normalized to pH 8, according to USEPA 1999) were 

16.95 mg TAN/L for the 30-day juvenile fathead growth test and 8.62 mg TAN/L for the 32-day 

embryo-larval survival and growth test. Using the relationship from the results obtained between 

juvenile Topeka shiners and juvenile (growth) and embryo-larval test using fathead minnows 

(growth and survival), a 32-day embryo-larval study with Topeka shiner might be expected to 

result in a chronic value that is approximately 51% more sensitive than the 30-day juvenile 

growth test with that species, or a chronic value of approximately 5.63 mg TAN/L (i.e., the 
170

reported 30-day MATC of 11.10 mg TAN/L at pH 8 based on growth of juvenile Topeka shiners 

multiplied by a factor of 0.507). Using EPA’s TRAP (version 1.21a) the 32-day biomass EC20

for embryo-larval fathead minnow (measured from days 7-32), 30-day adult survival EC20 for 

Topeka shiner, and 30-day juvenile specific growth rate EC20 for Topeka shiner were 7.457, 

10.85, and 6.483 mg TAN/L at test temperatures (25.5, 23.9, and 12.4°C) and pH (7.95, 7.94, 

and 8.07), respectively. When adjusted to pH 7, the EC20s for the respective tests are 16.87 mg 

TAN/L for the fathead minnow (Appendix B), and 24.21 and 17.45 mg TAN/L for the Topeka 

shiner (Appendix C), much higher than the 2013 chronic criterion.

Chronic Toxicity Data for Amphibians

In a long term chronic study by Jofre and Karasov (1999), pre-metamorphic (Gosner 

stage 24-26) green frog (Rana clamitans) tadpoles were exposed to ammonia for 103 days under 

renewal conditions. Tadpoles were evaluated in two different experiments conducted in 

successive years. In the 1997 (repeat) experiment, survival and growth were not statistically 

different from controls at the highest concentration tested, or 2.2 mg TAN/L at pH 8.7 and 24°C, 

although only approximately 50 percent of the frogs survived at this concentration compared to 

the controls (98 percent survival). Survival was reduced to approximately 78 percent at 0.9416

mg TAN/L at test temperature and pH (or 7.149 mg TAN/L at pH 7). Growth, measured as total 

length, was no different between treatments. The frogs grew from an average total length of 

approximately 7.5 mm at test initiation to approximately 50 mm in all treatments. The NOEC 

for growth of green frog tadpoles in the study (which does not reflect an ELS or partial life cycle

test) is >16.74 mg TAN/L at pH 7.
171

Appendix J. Unused Acute Studies Potentially Influential for Freshwater Ammonia Criteria Development.

Appendix J. Unused Acute Studies Potentially Influential for Freshwater Ammonia Criteria Development

Reference: Organism:

Reported or Normalized Acute 

Value Expressed as Total 

Ammonia (mg TAN/L) at pH=7

and 20°C, Where Applicable Rationale for Omission:

Abdalla, A.A.F. and C.D. McNabb. 1999. Acute and 

sublethal growth effects of unionized ammonia to Nile 

tilapia Oreochromis niloticus. In: Nitrogen production 

and excretion in fish. Randall D.J. and D.D. Mackinlay 

(Eds.), Department of Fisheries and Oceans, Vancouver, 

BC, Canada and Towson University, Baltimore, MD. 

pp. 35-48.

Oreochromis niloticus Normalized LC50 = 87.0

Species is a resident, non-North American 

"invasive" species known to cause or likely to cause 

economic or environmental harm (see ISAC 2006). 

Because the species is in the Family Centrarchidae 

which is well represented in the current acute 

criteria dataset, it has been intentionally excluded 

from further consideration and calculation of an 

acute criterion.

Alonso, A. and J.A. Camargo. 2011. The freshwater 

planarian Polycelis felina as a sensitive species to assess 

the long-term toxicity of ammonia. Chemosphere 84: 

533-537.

Polycelis felina Normalized 96 h LC50 = 25.72 Species not resident in North America.

Ankley, G.T., M.K. Schubauer-Berigan and P.D. 

Monson. 1995. Influence of pH and hardness on toxicity 

of ammonia to the amphipod Hyalella azteca. Can. J. 

Fish. Aquat. Sci. 52(10): 2078-2083.

Hyalella azteca

Normalized 96 h LC50s:

Softwater (Lake Superior) -

25.51 (pH 6.50)

47.35 (pH 7.49)

233.4 (pH 8.21)

Hardwater (Reconstituted-ASTM) -

232.8 (pH 6.55)

337.6 (pH 7.41)

545.5 (pH 8.45)

Ankley et al. conducted several static-renewal acute 

tests with H. azteca to determine the effect of pH 

and hardness on the toxicity of ammonia. For the 

hardness evaluation, Ankley chose three waters for 

testing, soft water (SW; unaltered lake Superior 

water), moderately hard water (MW; hardened Lake 

Superior water), and hard water (HW; hard 

reconstituted water). At the time, Ankley et al. 

focused only on hardness in the test waters, but the 

ion ratios in these three waters were not consistent. 

Of the three water types, only the moderately hard 

water (MW) that Ankley used is suitable for testing 

and culturing amphipods (see Appendix A for 

results). The SW was not suitable for testing this 

species because the sodium concentration was too 

low. Similarly, the reconstituted HW was not 

suitable because the bromide was too low. Bold 

values indicate LC50s below the cutoff of 93 mg 

TAN/L for unused, potentially influential acute 

values. 
172

Appendix J. Unused Acute Studies Potentially Influential for Freshwater Ammonia Criteria Development

Reference: Organism:

Reported or Normalized Acute 

Value Expressed as Total 

Ammonia (mg TAN/L) at pH=7

and 20°C, Where Applicable Rationale for Omission:

Augspurger, T., A.E. Keller, M.C. Black, W.G. Cope 

and F.J. Dwyer. 2003. Water quality guidance for 

protection of freshwater mussels (Unionidae) from 

ammonia exposure. Environ. Toxicol. Chem. 22(11): 

2569-2575.

Medionidus conradicus Normalized 48 h LC50 = 27.56 48-hr glochidia test. Secondary data from Keller 

2000

Babu, T.R., P. Surendranath and K.V. Ramana Rao. 

1987. Comparative evaluation of DDT and fenvalerate 

toxicity on Penaeus indicus (H. Milne Edwards). 

Mahasagar 20(4): 249-253.

Daphnia magna

Reported LC50s:

60 (25 h),

32 (50 h), 

20 (100 h)

pH not reported – LC50s could not be normalized. 

Belanger, S.E., D.S. Cherry, J.L. Farris, K.G. 

Sappington and J.J. Cairns. 1991. Sensitivity of the 

Asiatic clam to various biocidal control agents. J. Am. 

Water Works Assoc. 83(10): 79-87.

Corbicula fluminea

Normalized LC50s:

23.55 (4.1 d)

64.99 (4.2 d)

Species is a resident, non-North American 

"invasive" species known to cause or likely to cause 

economic or environmental harm (see ISAC 2006). 

This species is the target of current eradication and 

control programs in various states, and because this 

Phylum (Mollusca) is well represented in the current 

acute criteria dataset, this species has been 

intentionally excluded from further consideration 

and calculation of an acute criterion.

Dehedin, A., C. Piscart and P. Marmonier. 2012. 

Seasonal variations of the effect of temperature on lethal 

and sublethal toxicities of ammonia for three common 

freshwater shredders. Chemopshere In press. 

Gammarus pulex

Normalized 96h LC50s:

36.98 

49.31

49.31

69.40

Species not resident in North America. Control 

mortality less than 15%.

Gammarus roeselii

Normalized 96 h LC50s:

2.466

24.66

36.98

46.27

46.27

55.31

55.31

57.84

Species not resident in North America. Control 

mortality less than 15%.
173

Appendix J. Unused Acute Studies Potentially Influential for Freshwater Ammonia Criteria Development

Reference: Organism:

Reported or Normalized Acute 

Value Expressed as Total 

Ammonia (mg TAN/L) at pH=7

and 20°C, Where Applicable Rationale for Omission:

Dowden, B.F. and H.J. Bennett. 1965. Toxicity of 

selected chemicals to certain animals. J. Water Pollut. 

Control Fed. 37(9): 1308-1316.

Daphnia magna

Reported LC50s:

202 (24 h), 

423 (25 h), 

161 (48 h), 

433 (50 h), 

67 (72 h), 

50 (96 h), 

202, 139 (100 h)

pH not reported – LC50s could not be normalized.

Lymnaea sp.

Reported LC50s:

241 (24 h), 

173 (48 h), 

73 (72 h), 

70 (96 h)

pH not reported – LC50s could not be normalized.

Ewell, W.S., J.W. Gorsuch, R.O. Kringle, K.A. 

Robillard and R.C. Spiegel. 1986. Simultaneous 

evaluation of the acute effects of chemicals on seven 

aquatic species. Environ. Toxicol. Chem. 5(9): 831-840.

Daphnia magna

Reported LC50 in paper = >100;

Reported LC50 in ECOTOX = >20

Normalized LC50 = 36.29

Insufficient controls; pH that varied from 6.5-8.5 

during the exposure. LC50 based on a 96 h (nonstandard) test duration. 

Fairchild, J.F., A. Allert, J. Mizzi, R. Reisenburg and B. 

Waddell. 1999. Determination of a safe level of 

ammonia that is protective of juvenile Colorado 

pikeminnow in the upper Colorado River, Utah. Final 

Report.1998 Quick Response Program. U.S. Fish and 

Wildlife Service, Region 2 (Salt Lake City Office).

Pimephales promelas Normalized LC50 = 60.12 72-hour test in well water

Hazel, R.H., C.E. Burkhead and D.G. Huggins. 1982. 

Development of water quality criteria for ammonia and 

total residual chlorine for the protection of aquatic life in 

two Johnson County, Kansas Streams. In: J.G. Pearson, 

R.B. Foster, and W.E. Bishop (Eds.), Proc. Annu. Symp. 

Aq. Tox., ASTM STP 766, Philadelphia, PA: 381-388.

Etheostoma spectabile Normalized 96 h LC50s = 83.74, 

71.12

Same data as in Hazel (1979) – see E. spectabile in 

Appendix A. 

Hecnar, S.J. 1995. Acute and chronic toxicity of 

ammonium nitrate fertilizer to amphibians from 

Southern Ontario. Environ. Toxicol. Chem. 14(12):

2131-2137. 

Pseudacris triseriata

Reported values:

4-d LC50 = 17

4-d NOEC = 5, 

4-d LOEC = 45

Formulation - ammonium nitrate fertilizer
174

Appendix J. Unused Acute Studies Potentially Influential for Freshwater Ammonia Criteria Development

Reference: Organism:

Reported or Normalized Acute 

Value Expressed as Total 

Ammonia (mg TAN/L) at pH=7

and 20°C, Where Applicable Rationale for Omission:

Hickey, C.W. and M.L. Vickers. 1994. Toxicity of 

ammonia to nine native New Zealand freshwater 

invertebrate species. Arch. Environ. Contam. Toxicol. 

26(3): 292-298.

Potamopyrgus 

antipodarum

Normalized 96 h LC50s:

33.14

29.79

38.93

36.27

Species is a resident, non-North American 

"invasive" species known to cause or likely to cause 

economic or environmental harm (see ISAC 2006). 

This species is the target of current eradication and 

control programs in various states, and because this 

Phylum (Mollusca) is well represented in the current 

acute criteria dataset, this species has been 

intentionally excluded from further consideration 

and calculation of an acute criterion.

Horne, F.R. and S. McIntosh. 1979. Factors influencing 

distribution of mussels in the Blanco River of Central 

Texas. Nautilus 94(4): 119-133.

Cyrtonaias tampicoensis Normalized LC50 = 26.75 LC50 based on a 7-d (non-standard) test duration.

Toxolasma texasensis Normalized LC50 = 26.75 LC50 based on a 7-d (non-standard) test duration.

Corbicula manilensis Normalized LC50 = 26.75 LC50 based on a 7-d (non-standard) test duration.

Jofre, M.B., and W.H. Karasov. 1999. Direct effect of 

ammonia on three species of North American anuran 

amphibians. Environ.Toxicol.Chem. 18(8): 1806-1812.

Bufo americanus Normalized 96 h LC50 = 62.85

Non-standard acute endpoint based on hatch 

success/ deformity.UIA calculated using Thurston et 

al. (1979) EPA-600/3-79-091 from measured values

Rana clamitans Normalized 96 h LC50 = 40.80

Non-standard acute endpoint based on hatch 

success/ deformity.UIA calculated using Thurston et 

al. (1979) EPA-600/3-79-091 from measured values

Jofre, M.B., M.L. Rosenshield and W.H. Karasov. 2000. 

Effects of PCB 126 and ammonia, alone and in 

combination, on green frog (Rana clamitans) and 

leopard frog (R. pipiens) hatching success, development, 

and metamorphosis. J. Iowa Acad. Sci. 107(3): 113-122.

Rana clamitans Normalized 96 h LC50 = 49.56

Non-standard acute endpoint based on hatch 

success/ deformity. pH not reported; assume same as 

Jofre and Karasov 1999.

Kaniewska-Prus, M. 1982. The Effect of ammonia, 

chlorine, and chloramine toxicity on the mortality of 

Daphnia magna Straus. Pol. Arch. Hydrobiol. 29(3/4):

607-624.

Daphnia magna Normalized LC50 = 1.980 LC50 based on a 24-h (non-standard) test duration.

Meyer, J.S. and J.A. Hansen. 2002. Subchronic toxicity 

of low dissolved oxygen concentrations, elevated pH, 

and elevated ammonia concentrations to Lost River 

suckers. Trans. Amer. Fish. Soc. 131: 656-666.

Deltistes luxatus Normalized 48 h LC50:

78.23

The pH for this test was reported as 9.5, which is 

outside of the acceptable pH range of (6.0-9.0) these 

criteria were meant to apply.

Morgan, W.S.G. 1979. Fish locomotor behavior patterns 

as a monitoring tool. J. Water Pollut. Control. Fed. 

51(3): 580-589.

Micropterus salmoides Normalized EC50 = 5.010

Acute toxicity evaluated electronically based on 

activity. Exposure was only 24-h (non-standard) in 

test duration. Concentrations were nominal.

Morgan, W.S.G. 1976. Fishing for toxicity: Biological 

automonitor for continuous water quality control. Effl. 

Water Treat. J. 16(9): 471-475.

Micropterus salmoides Normalized EC50 = 5.010

Added nominal concentrations equivalent to 48-h 

LC50 from previous literature values, then monitored 

opercular rhythm activity for 24 h.
175

Appendix J. Unused Acute Studies Potentially Influential for Freshwater Ammonia Criteria Development

Reference: Organism:

Reported or Normalized Acute 

Value Expressed as Total 

Ammonia (mg TAN/L) at pH=7

and 20°C, Where Applicable Rationale for Omission:

Morgan, W.S.G. and P.C. Kuhn. 1974. A method to 

monitor the effects of toxicants upon breathing rate of 

largemouth bass (Micropterus salmoides Lacepede). 

Water Res. 8(1): 67-77 

Micropterus salmoides 

Lacepede

Normalized EC50s:

110.3 (11 h), 

31.32 (22 h), 

110.3 (23 h), 

1.556 (44 h)

Similar to Morgan (1976). This is not an actual 

toxicity test. Rather, it is a test of a monitoring 

system that relates nominal LC50 concentrations 

(based on literature values), to breathing rate 

monitored over 24 h.

Morgan, W.S.G. 1978. The use of fish as a biological

sensor for toxic comparison in potable water. Prog. 

Water Tech. 10: 395-398. 

Micropterus salmoides Normalized LC50 = 9.091

Similar to other Morgan studies listed in this table

where nominal ammonia concentrations based on 

literature LC50 concentrations are added to tanks and 

breathing rate and activity level are monitored 

electronically for 24 h.

Passell, H.D., C.N. Dahm and E.J. Bedrick. 2007. 

Ammonia modeling for assessing potential toxicity to 

fish species in the Rio Grande, 1989-2002. Ecol. Appl. 

17(7): 2087-2099.

Hybognathus amarus

Secondary data; reported LC50 from 

Buhl 2002 = 1.01 mg/L unionized 

ammonia-N

In this study the frequency of acute ammonia 

exceedances were modeled by relating discharge, 

pH, temperature, and stream ammonia 

concentrations to literature LC50 values.

Scheller, J.L. 1997. The effect of dieoffs of Asian clams 

(Corbicula fluminea) on native freshwater mussels 

(Unionidae). Virginia Polytechnic Institute and State 

University, Blacksburg, VA.

Corbicula fluminea

Normalized LC50s:

6.498 (96 h)

11.57 (96 h)

14.62 (96 h)

Species is a resident, non-North American 

"invasive" species known to cause or likely to cause 

economic or environmental harm (see ISAC 2006). 

This species is the target of current eradication and 

control programs in various states, and because this 

Phylum (Mollusca) is well represented in the current 

acute criteria dataset, this species has been 

intentionally excluded from further consideration 

and calculation of an acute criterion.

Pimephales promelas Normalized LC50 = 38.46 Non-standard (48 h) test duration.

Watton, A.J. and H.A. Hawkes. 1984. The acute toxicity 

of ammonia and copper to the gastropod Potamopyrgus 

jenkinsi (Smith). Environ. Pollut. Ser. A 36: 17-29.

Potamopyrgus jenkinsi

Normalized EC50s:

40.31 and 42.06 (48 h), 

27.60 and 27.17 (96 h)

Species not resident in North America.
176

Appendix J. Unused Acute Studies Potentially Influential for Freshwater Ammonia Criteria Development

Reference: Organism:

Reported or Normalized Acute 

Value Expressed as Total 

Ammonia (mg TAN/L) at pH=7

and 20°C, Where Applicable Rationale for Omission:

Whiteman, F.W., G.T. Ankley, M.D. Kahl, D.M. Rau 

and M.D. Balcer. 1996. Evaluation of interstitial water 

as a route of exposure for ammonia in sediment tests 

with benthic macroinvertebrates. Environ. Toxicol.

Chem. 15(5): 794-801.

Hyalella azteca

Normalized 96 h LC50s:

10.27 (Lake Superior water)

11.06 (sediment test)

72.67 (sediment test)

Tests were fed. The results from the two sediment 

tests were not used because sediment toxicity tests 

using pore water measurements likely underestimate 

the toxicity of ammonia in a water-only exposure, 

i.e., test animals could have been exposed to the 

higher interstitial ammonia concentrations during 

the exposurea. The 96 h LC50 for H. azteca from 

water-only exposure to Lake Superior water was not 

used from this study because the sodium 

concentration in this dilution water is too low for 

maintaining adequate animal health – see also the 

results in this appendix from Ankley et al. (1995) 

above. 

a For the same reason the sediment tests reported by Whiteman et al. (1996) for H. azteca were unused for criteria derivation, results from the sediment tests from Besser et al. 

(1998) were also not used. The normalized 96 h LC50s for H. azteca from the Besser et al. (1998) sediment tests were 120.5 and 321.4 mg TAN/L at pH 6.69 and 7.56, 

respectively. Two other LC50s generated for H. azteca which are also not used for criteria derivation (due to the insufficient amount of detail provided) include values of 251.5 and 

262.7 mg TAN/L from Sarda (1994). Because these latter values exceed 93 mg TAN/L, they are considered non-influential data for the purpose of criteria derivation.
177

Appendix K. Unused Chronic Studies Potentially Influential for Freshwater Ammonia Criteria Development.

Appendix K. Unused Chronic Studies Potentially Influential for Freshwater Ammonia Criteria Development

Reference: Organism:

Reported or Normalized Chronic Value 

Expressed as Total Ammonia (mg 

TAN/L) at pH=7 and 20°C, Where 

Applicable Rationale for Omission:

El-Shafai, S.A., F.A. El-Gohary, F.A. Nasr, N.P. 

Vander Steen and H.J. Gijzen. 2004. Chronic 

ammonia toxicity to duckweed-fed tilapia 

(Oreochromis niloticus). Aquacult. 232(1-4): 117-

127.

Oreochromis 

niloticus Normalized Chronic value = 6.881 (75 d)

Test was a 35-day juvenile test; not a true fish ELS 

test. Species is also a resident, non-North American 

"invasive" species known to cause or likely to cause 

economic or environmental harm (see ISAC 2006).

DeGraeve, G.M., W.D. Palmer, E.L. Moore, J.J. 

Coyle and P.L. Markham. 1987. The effect of 

temperature on the acute and chronic toxicity of 

unionized ammonia to fathead minnows and channel 

catfish. Battelle, Columbus, OH.

Ictalurus punctatus Normalized 30-day NOEC = 0.5628

Per the 1999 update, this 30-day test with juvenile 

catfish encountered some problems that precluded 

effective use of these data. For example, some of 

the test organisms were treated with acriflavine up 

to two days prior to the beginning of the test. In 

addition, the mean measured DO concentration was 

below 5.5 mg/L and below 60 percent of saturation 

in some of the treatments.

Hecnar, S.J. 1995. Acute and chronic toxicity of 

ammonium nitrate fertilizer to amphibians from 

Southern Ontario. Environ. Toxicol. Chem. 14(12):

2131-2137. 

Pseudacris 

triseriata

Reported values:

100-d NOEC = 2.5,

100-d LOEC = 10

Formulation - ammonium nitrate fertilizer.

Hermanutz, R.O., S.F. Hedtke, J.W. Arthur, R.W. 

Andrew and K.N. Allen. 1987. Ammonia effects on 

macroinvertebrates and fish in outdoor experimental 

streams. Environ. Pollut. 47: 249-283.

Ictalurus punctatus Normalized NOEC = 4.369

Survival and growth of juvenile channel catfish 

were evaluated via exposure to ammonia in 

experimental streams. Three separate tests lasted 

from 36 to 177 days and were started with 

individuals whose average weights ranged from 6 

to 19 g. Average temperatures in the three tests 

were 17 to 21°C. Both of the longer tests showed 

monotonic, substantial reductions in biomass; these 

results are in reasonable agreement with the results 

of the laboratory tests. However, juveniles might 

not be as sensitive to ammonia toxicity as early life 

stages are. These results are not included because 

they are from a field study where ammonia 

concentrations were highly variable.

Sander vitreus Normalized NOEC = 4.182 Omitted for the same reasons as was Ictalurus 

punctatus.
178

Appendix K. Unused Chronic Studies Potentially Influential for Freshwater Ammonia Criteria Development

Reference: Organism:

Reported or Normalized Chronic Value 

Expressed as Total Ammonia (mg 

TAN/L) at pH=7 and 20°C, Where 

Applicable Rationale for Omission:

Hickey, C.W., L.A. Golding, M.I. Martin and G.F. 

Croker. 1999. Chronic toxicity of ammonia to New 

Zealand freshwater invertebrates: A mesocosm 

study. Arch. Environ. Contam. Toxicol. 37:338-351.

Deleatidium sp.

(Ephemeroptera)

Normalized 29-day EC25 (survival) = 

3.844

Species not resident in North America. These 

results are not included because they are from a 

field study where ammonia concentrations were 

highly variable.

Rice, S.D. and J.E. Bailey. 1980. Survival, size, and 

emergence of pink salmon, Oncorhynchus 

gorbuscha, alevins after short- and long-term 

exposures to ammonia. Fish. Bull. 78(3):641-648.

Oncorhynchus 

gorbuscha Normalized 61-d NOEC = 5.859

Per the 1999 update, the only chronic test began 

sometime after hatch and ended when the alevins 

emerged (i.e., at the beginning of swim-up); 

therefore the test did not include effects of 

ammonia on the growth and survival of fry after 

feeding started. In addition, no information was 

given concerning survival to the end of the test in

the control or any other treatment. This test did not 

provide data concerning survival and is not an ELS 

test because it began after hatch.

Schulter, M. and J. Groeneweg. 1985. The inhibition 

by ammonia of population growth of the rotifer, 

Brachionus rubens, in continuous culture.

Aquaculture 46: 215-220.

Brachionus rubens Normalized 7-d NOEC = 3.000

Species is not resident in North America. Generally 

a marine Rotifera. Undescribed culture medium. 

NOEC based on population growth of cultures.

Smith, C.E. 1972. Effects of metabolic products on 

the quality of rainbow trout. Am. Fish. Trout News 

17:7-8.

Oncorhynchus 

mykiss Normalized 84-d NOEC = 2.304

This test did not provide data concerning survival 

and is not an ELS test because it began after hatch. 

The authors reported that as long as the DO 

concentration was maintained at 5 mg/L or greater, 

growth of young rainbow trout was not 

significantly reduced until average total ammonia 

concentrations reached 1.6 mg TAN/L at test pH 

and temperature (7.75 and 10°C, respectively).

Zischke, J.A. and J.W. Arthur. 1987. Effects of 

elevated ammonia levels on the fingernail clam, 

Musculium transversum, in outdoor experimental 

streams. Arch. Environ. Contam. Toxicol. 16(2):

225-231.

Musculium 

transversum

Normalized LOEC = 6.933 (survival)

This was a flow-through, measured mesocosm 

experiment performed in the field. The test 

concentrations varied during the length of the 

experiment.
179

Appendix L. Unused (Non-Influential) Acute and Chronic Studies for Freshwater 

Ammonia Criteria Development – Screened Out Studies with Code List.

(appears separately at end of appendix)

Appendix L. Unused (Non-influential) Acute and Chronic Studies for Freshwater Ammonia Criteria Development

Citation

ECOTOX or 

Other

Ref. No

Rejection

Code(s) Comment(s)

Academy of Natural Sciences. 1960. The sensitivity of 

aquatic life to certain chemicals commonly found in 

industrial wastes. Final Report No. RG-3965 (C2R1). U.S.

Public Health Service Grant, Academy of Natural 

Sciences, Philadelphia, PA. 5683 AF

Alabaster, J.S., D.G. Shurben and G. Knowles. 1979. The 

effect of dissolved oxygen and salinity on the toxicity of 

ammonia to smolts of salmon, Salmo salar L. J. Fish

Biol.15(6): 705-712 (Personal Communication Used). 406 Dur - 1d

Alabaster, J.S., D.G. Shurben and M.J. Mallett. 1983. The 

acute lethal toxicity of mixtures of cyanide and ammonia to 

smolts of salmon, Salmo salar L. at low concentrations of 

dissolved oxygen. J. Fish Biol. 22: 215-222. 10252 Dur - 1d

Alam, M., T.L. Frankel and M. Alam. 2006. Gill ATPase 

activities of silver perch, Bidyanus bidyanus (Mitchell), and 

golden perch, Macquaria ambigua (Richardson): Effects of 

environmental salt and ammonia. Aquaculture 251(1): 118-

133. 84839 NonRes

Allan, I.R.H., D.W.M. Herbert and J.S. Alabaster. 1958. A 

field and laboratory investigation of fish in a sewage 

effluent. Minist. Agric. Fish. Food, Fish. Invest. Ser. 1. 6(2):

76. 10316 AF, Det

Alonso, A. and J.A. Camargo. 2003. Short-term toxicity to 

ammonia, nitrite, and nitrate to the aquatic snail 

Potamopyrgus antipodarum (Hydrobiidae, Mollusca). Bull. 

Environ. Contam. Toxicol. 70: 1006-1012 INV

Alonso, A. and J.A. Camargo. 2006. Ammonia toxicity to 

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Armstrong, D.A. 1978. Toxicity and metabolism of nitrogen 

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Ph.D. Thesis, University of California, Davis, CA. (Personal 

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Bailey, H.C., C. DiGiorgio, K. Kroll, J.L. Miller, D.E. Hinton

and G. Starrett. 1996. Development of procedures for 

identifying pesticide toxicity in ambient waters: 

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15(6): 837-845. 16844 AF

Ball, I.R. 1967. The relative susceptibilities of some 

species of fresh-water fish to poisons - I. Ammonia. Water 

Res. 1(11/12): 767-775. 10000 Dur

Banerjee, S. and S. Bhattacharya. 1994. Histopathology of 

kidney of Channa punctatus exposed to chronic nonlethal 

level of elsan, mercury, and ammonia. Ecotoxicol. Environ.

Saf. 29(3): 265-275. 13750

NonRes, Eff, 

UEndp
180

Appendix L. Unused (Non-influential) Acute and Chronic Studies for Freshwater Ammonia Criteria Development

Citation

ECOTOX or 

Other

Ref. No

Rejection

Code(s) Comment(s)

Banerjee, S. and S. Bhattacharya. 1995. Histopathological 

changes induced by chronic nonlethal levels of elsan, 

mercury, and ammonia in the small intestine of Channa 

punctatus (Bloch). Ecotoxicol. Environ. Saf. 31(1): 62-68. 15256

NonRes, Eff, 

UEndp

Banerjee, S. and S. Bhattacharya. 1997. Histopathological 

changes induced by chronic nonlethal levels of elsan, 

mercury and ammonia in the liver of Channa punctatus

(Bloch). J. Environ. Biol. 18(2): 141-148. 18229

NonRes, Eff, 

UEndp

Banerjee, T.K. and V.I. Paul. 1993. Estimation of acute 

toxicity of ammonium sulphate to the fresh water catfish, 

Heteropneustes fossilis II. A histopathological analysis of 

the epidermis. Biomed. Environ. Sci. 6(1): 45-58. 13480 NonRes, UEndp

Batley, G.E. and S.L. Simpson. 2009. Development of 

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systems. Mar. Pollut. Bull. 58(10): 1472-1476. Dilut Salt water

Bergerhouse, D.L. 1989. Lethal effects of elevated pH and 

ammonia on early life stages of several sportfish species. 

Ph.D. Thesis, Southern Illinois University, Carbondale, IL. 3822 UEndp, Dur - 8h

Bergerhouse, D.L. 1992. Lethal effects of elevated pH and 

ammonia on early life stages of walleye. N. Am. J. Fish.

Manage. 12(2): 356-366. 6903 UEndp, Dur - 8h

Bergerhouse, D.L. 1993. Lethal effects of elevated pH and 

ammonia on early life stages of hybrid striped bass. J.

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Bhattacharya, T., S. Bhattacharya, A.K. Ray and S. Dey. 

1989. Influence of industrial pollutants on thyroid function 

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68. 3106

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as the key factor for optimization of stocking density of 

common carp in small holding tanks. Aquaculture 261(3):

952-959. 

No Dose, 

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fish density in a shallow lake: A mesocosm experiment. 

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Braun, M.H., S.L. Steele and S.F. Perry. 2009. The 

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Zostera noltii to stress caused by low light and elevated 

ammonium levels under phosphate deficiency. Mar. Ecol.

Prog. Ser. 365: 67-75. Tox
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Appendix L. Unused (Non-influential) Acute and Chronic Studies for Freshwater Ammonia Criteria Development

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Watt, P.J. and R.S. Oldham. 1995. The effect of 

ammonium nitrate on the feeding and development of 

larvae of the smooth newt, Triturus vulgaris (L.), and on the 

behaviour of its food. Freshw. Biol. 33(2): 319-324. 14883 UEndp

Wee, N.L.J., Y.Y.M. Tng, H.T. Cheng, S.M.L. Lee, S.F. 

Chew and Y.K. Ip. 2007. Ammonia toxicity and tolerance in 

the brain of the African sharptooth catfish, Clarias 

gariepinus. Aquat. Toxicol. 82(3): 204-213. 

NonRes, No 

Dose Only 2 exposure concentrations

Weiss, L.A. and E. Zaniboni-Filho. 2009. Survival of diploid 

and triploid Rhamdia quelen juveniles in different ammonia 

concentrations. Aquaculture 298(1-2): 153-156. NonRes

Wells, M.M. 1915. The reactions an resistance of fishes in 

their natural environment to salts. J. Exp. Zool. 19(3): 243-

283. Det, No Dose

Wickins, J.F. 1976. The tolerance of warm-water prawns to 

recirculated water. Aquaculture 9(1): 19-37. 2320 AF, UEndp, Dur

Wilkie, M.P., M.E. Pamenter, S. Duquette, H. Dhiyebi, N. 

Sangha, G. Skelton, M.D. Smith and L.T. Buck. 2011. The 

relationship between NMDA receptor function and the high 

ammonia tolerance of anoxia-tolerant goldfish. J. Exp. Biol. 

214(24): 4107-4120. Eff, UEndp

Williams, J.E. Jr. 1948. The toxicity of some inorganic salts 

to game fish. M.S. Thesis, Louisiana State University, 

Baton Rouge, LA, 71 p. No Org
196

Appendix L. Unused (Non-influential) Acute and Chronic Studies for Freshwater Ammonia Criteria Development

Citation

ECOTOX or 

Other

Ref. No

Rejection

Code(s) Comment(s)

Woltering, D.M., J.L. Hedtke and L.J. Weber. 1978. 

Predator-prey interactions of fishes under the influence of 

ammonia. Trans. Am. Fish. Soc. 107(3): 500-504. 7218 UEndp, Dur

Xu, Q. and R.S. Oldham. 1997. Lethal and sublethal 

effects of nitrogen fertilizer ammonium nitrate on common 

toad (Bufo bufo) tadpoles. Arch. Environ. Contam. Toxicol. 

32(3): 298-303. 17840 AF, UEndp, Dur

Zhang, L. and C.M. Wood. 2009. Ammonia as a stimulant 

to ventilation in rainbow trout Oncorhynchus mykiss. 

Respir. Physiol. Neurobiol. 168(3): 261-271. RouExp

Zhang, L.J., G.G. Ying, F. Chen, J.L. Zhao, L. Wang and 

Y.X. Fang. 2012. Development and application of wholesediment toxicity test using immobilized freshwater 

microalgae Pseudokirchneriella subcapitata. Environ. 

Toxicol. Chem. 31(2): 377-386. SedExp Plant
197

Corresponding Code List

ABIOTIC FACTOR

(AF)

Studies where one or both of the two abiotic factors (pH and temperature) important for ammonia criteria 

derivation are not reported.

ACELLULAR

(Ace) Studies of acellular organisms (protozoa) and yeast.

BACTERIA

(Bact) Studies describing only the results on bacteria.

BIOMARKER

(Biom)

Studies reporting results for a biomarker having no reported association with a biologically significant 

adverse effect (survival, growth, or reproduction of an individual or population) and an exposure dose (or 

concentration).

CONTROL

(Con)

Studies where control mortality is insufficient or unsatisfactory, i.e., where survival is less than 90% in 

acute tests or 80% in chronic tests; or where no control is used.

DETAIL

(Det)

Insufficient detail regarding test methodology or statistical analysis.

DURATION

(Dur)

Laboratory and field studies where duration of exposure is inappropriate (e.g., too short) for the type of 

test (i.e., acute or chronic), or was not reported or could not be easily estimated.

EFFLUENT 

(Efflu)

Studies reporting only effects of effluent, sewage, or polluted runoff where individual pollutants are not 

measured.

EFFECT

(Eff)

Studies where the biologically significant adverse effect was not survival, growth, or reproduction of an 

individual or population.

ENDPOINT

(UEndp)

Studies reported in ECOTOX where an endpoint (LC50, EC50, NOEC, LOEC, MATC, EC20, etc.) was 

not provided, where none of the concentrations tested in a chronic test were deleterious (no LOEC); or 

where all concentrations tested in a chronic test caused a statistically significant adverse effect (no 

NOEC).

FIELD

(Field)

Chronic, long-term studies conducted in a field setting (stream segment, pond, etc.) where source/dilution 

water is not characterized for other possible contaminants.

FORMULATION

(Form)

Studies where the chemical is a primary ingredient in a commercial formulation, e.g., biocide, fertilizer, 

etc.

INVASIVE [Harmful]

(INV)

Defined in this document as a species that is non-native to the ecosystem under consideration and 

whose introduction causes or is likely to cause economic or environmental harm or harm to human health 

(see ISAC 2006).

IN VITRO

(In Vit)

In vitro studies, including only exposure of the chemical to cell cultures and excised tissues and not 

related to whole organism toxicity.

LETHAL TIME

(LT)

Laboratory studies reporting only lethal time to mortality, except under special conditions (no other 

applicable information is available for species pivotal in making a finding).

NO DOSE or CONC

(No Dose or Conc)

Studies with too few concentrations to establish a dose-response, or no usable dose or concentration 

reported in either primary or sister article(s), except under special conditions (no other applicable 

information is available for species pivotal in making a finding).

NOMINAL

(Nom) Chronic studies where test concentrations were not measured.

NON-RESIDENT

(NonRes)

Species that are not resident to North America, or where there is no reported evidence of their 

reproducing naturally in North America.

NO ORGANISM

(No Org)

Laboratory and field studies where no one organism is studied (e.g., periphyton community) or where no 

scientific/common name is given in either a primary or sister article(s). 

PURITY

(Pur) Studies where the chemical purity of the toxicant was less than 80% pure (active ingredient).

ROUTE OF EXPOSURE

(RouExp) Dietary or un-natural exposure routes for aquatic chemicals, e.g., injection, spray, inhalation.

Secondary

(Sec) Non-original data first reported elsewhere.

Sediment Exposure

(SedExp) Sediment-based toxicity test and method.

TOXICANT

(Tox)

Inappropriate form of toxicant used or none identified in a laboratory or field study. Note: Inappropriate 

form includes mixtures.

UNACCEPTABLE CHRONIC

(UChron)

Chronic studies which were not based on flow-through exposures (exception for cladocerans and other 

small, planktonic organisms where test water is continuously renewed), where test concentrations were 

not measured, or when the chronic test did not include the appropriate test duration for the organism and 

life-stage tested.
198

UNUSUAL DILUTION 

WATER

(Dilut)

Laboratory or field studies where the dilution water contained unusual amounts or ratios of inorganic ions 

or was without addition of appropriate salts (i.e., distilled or de-ionized water).

VARIABLE EXPOSURE

(VarExp) Excessive variability in contaminant concentrations during the exposure period.

WATER QUALITY

(WatQual)

Studies where the measured test pH is below 6 or greater than 9, where dissolved oxygen was less than 

40% saturation for any length of time, or where total or dissolved organic carbon is greater than 5 mg/L.
199

Appendix M. 1999 Re-examination of Temperature Dependence of Ammonia Toxicity.

This section presents the temperature analysis published in the 1998 Update, followed by 

the re-analysis performed for the 1999 Update and reproduced here as background information. 

Figure and table numbers are preceded by an ‘M’ in this appendix, in order to distinguish them 

from tables and figures in the main document.

1998 Analysis of Temperature-Dependence

The 1984/1985 ammonia criteria document identified temperature as an important factor 

affecting the toxicity of ammonia. When expressed in terms of unionized ammonia, the acute 

toxicity of ammonia was reported in the criteria document to be inversely related to temperature 

for several species of fish, whereas limited data on acute ammonia toxicity to invertebrates 

showed no significant temperature dependence. No direct data were available concerning the 

temperature dependence of chronic toxicity. It was noted, however, that the differences between 

chronic values for salmonid fish species tested at low temperatures and chronic values for 

warmwater fish species tested at higher temperatures paralleled differences in acute toxicity 

known to be caused by temperature. 

In the 1984/1985 criteria document, an average temperature relationship observed for fish 

was used to adjust fish acute toxicity data to a common temperature (20°C) for derivation of the 

CMC for unionized ammonia; this same relationship was used to extrapolate this CMC to other 

temperatures. (Invertebrate toxicity data were not adjusted, but invertebrates were sufficiently 

resistant to ammonia that adjustment of invertebrate data was not important in the derivation of 

the CMC.) This temperature relationship for fish resulted in the unionized ammonia CMC being 

higher at warm temperatures than at cold temperatures. Additionally, because of concerns about 

the validity of extrapolating the temperature relationship to high temperatures, the unionized 

ammonia CMC was "capped" to be no higher than its value at a temperature, called TCAP, near 

the upper end of the temperature range of the acute toxicity data available for warmwater and 
200

coldwater fishes. Similarly, the CCC was capped at a temperature near the upper end of the 

temperature range of the available chronic toxicity data.

Although the unionized ammonia criterion is lower at low temperatures, this does not 

result in more restrictive permit limits for ammonia because the ratio of ammonium ion to 

unionized ammonia increases at low temperatures, resulting in the total ammonia criterion being 

essentially constant at temperatures below TCAP. In practice, however, the criterion at low 

temperatures can be more limiting for dischargers than the criterion at high temperatures because 

biological treatment of ammonia is more difficult at low temperatures. Above TCAP, the 

constant unionized ammonia criterion results in the total ammonia criterion becoming 

progressively lower with increasing temperature, which can also result in restrictive discharge 

limitations.

Because more data are available at moderate temperatures than at lower and higher 

temperatures, the ammonia criterion is most uncertain for circumstances when compliance can 

be most difficult, either because of the low total ammonia criterion at high temperatures or 

because of treatment difficulties at low temperatures. This section examines the data used in the 

1984/1985 criteria document and newer data to determine (1) whether the use of TCAPs should 

be continued and (2) whether a lower unionized criterion at low temperature is warranted. Data 

used include those analyzed by Erickson (1985), which are shown in Figure 2 of the 1984/1985 

document, and more recent data reported by Arthur et al. (1987), DeGraeve et al. (1987), Nimmo 

et al. (1989), and Knoph (1992).

Data not used include those reported by the following:

1. Bianchini et al. (1996) conducted acute tests at 12 and 25°C, but one test was in fresh 

water, whereas the other was in salt water.

2. Diamond et al. (1993) conducted acute and chronic toxicity tests on ammonia at 12 and 

20°C using several vertebrate and invertebrate species. When expressed in terms of 

unionized ammonia, they reported that vertebrates (i.e., fishes and amphibians) were 

more sensitive to ammonia at 12°C than at 20°C, whereas invertebrates were either less 
201

sensitive or no more sensitive at 12°C, compatible with the relationships used in the 

1984/1985 criteria document. However, such factors as dilution water and test duration 

varied between tests at different temperatures and possibly confounded the results (see 

Appendix 1 of the 1999 update), raising doubts about the temperature comparisons for 

the vertebrates and invertebrates.

Arthur et al. (1987) measured the acute toxicity of ammonia to several fish and 

invertebrate species at ambient temperature during different seasons of the year. For three of the 

five fish species (rainbow trout, channel catfish, and white sucker), the relationship of toxicity to 

temperature was similar to that used in the 1984/1985 criteria document. When expressed in 

terms of unionized ammonia, no clear relationship existed between temperature and toxicity for 

the other fish species (fathead minnow and walleye). This result for the fathead minnow is 

different from those of three other studies (Reinbold and Pescitelli 1982b; Thurston et al. 1983; 

DeGraeve et al. 1987) reporting a significant effect of temperature on the acute toxicity of 

unionized ammonia to the fathead minnow. For five invertebrate species, each tested over a 

temperature range of at least 10°C, there was no consistent relationship between temperature and 

unionized ammonia toxicity. An initial report of these results (West 1985) was the basis for no 

temperature adjustment being used for invertebrate data in the 1984/1985 criteria document. 

Further analysis of the Arthur (1987) data is discussed later.

DeGraeve et al. (1987) studied the effect of temperature (from 6 to 30°C) on the toxicity 

of ammonia to juvenile fathead minnows and channel catfish using acute (4-day) and chronic 

(30-day) ammonia exposures. As shown for both fish species in Figure M.1, log(96-hr unionized 

ammonia LC50) versus temperature was linear within the reported uncertainty in the LC50s; the 

slopes were similar to those reported in the 1984/1985 criteria document. Problems with the 

channel catfish chronic tests precluded effective use of those data and the highest tested 

ammonia concentrations in the fathead minnow chronic tests at 15 and 20°C did not cause 

sufficient mortality to be useful. However, sufficient mortality did occur in the fathead minnow 

chronic tests at 6, 10, 25, and 30°C. Based on regression analysis of survival versus log 
202

concentration (discussed in more detail in the section concerning the CCC below), 30-day LC20s 

for unionized ammonia were 0.11, 0.18, 0.48, and 0.44 mg N/L at 6, 10, 25, and 30°C, 

respectively. This temperature dependence (Figure M.1) is similar to that for acute toxicity and 

that used in the 1984/1985 criteria document. The actual effect of temperature on these 30-day 

LC20s is probably somewhat greater, because test pH decreased with increasing temperature.

Nimmo et al. (1989) conducted acute toxicity tests on ammonia at 6 and 20°C in a well 

water using Johnny darters and in a river water using both Johnny darters and juvenile fathead 

minnows. In all three sets of tests, LC50s expressed in terms of unionized ammonia were 

significantly higher at the warmer temperature, by factors ranging from 3.5 to 6.2.

Knoph (1992) conducted acute toxicity tests at temperatures ranging from 2 to 17°C 

using Atlantic salmon parr, one series of tests at pH≈6.0 and the other at pH≈6.4. In both series 

of tests, LC50s expressed in terms of unionized ammonia increased substantially with 

temperature.

Even with these additional data, the shape of the temperature relationship is not 

completely resolved, especially for chronic toxicity. Nevertheless, the acute data for fishes 

overwhelmingly indicate that ammonia toxicity, expressed in terms of unionized ammonia, 

decreases with increasing temperature. 
203

Figure M.1. The Effect of Temperature on Ammonia Toxicity in Terms of Unionized Ammonia (DeGraeve et al. 1987).

Symbols denote LC50s or LC20s and 95% confidence limits and lines denote linear regressions of log LC versus temperature.

Temperature (C)

0 5 10 15 20 25 30 Un-ionized Ammonia (mg N/L)

0.2

0.4

0.6

0.8

2

4

0.1

1

Temperature (C)

0 5 10 15 20 25 30 Un-ionized Ammonia (mg N/L) 0.2

0.4

0.6

0.8

2

4

0.1

1

Temperature (C)

0 5 10 15 20 25 30 Un-ionized Ammonia (mg N/L) 0.06

0.08

0.2

0.4

0.6

0.8

2

0.1

1

Fathead Minnow

96-hr LC50

Channel Catfish

96-hr LC50

Fathead Minnow

30-day LC20
204

Most importantly, the data of DeGraeve et al. (1987) show (Figure M.1) that (a) a linear 

relationship of log unionized ammonia LC50 versus temperature applies within the reported 

uncertainty in the LC50s over the range of 6 to 30°C and (b) temperature effects on long-term 

mortality are similar to those on acute mortality. For invertebrates, acute toxicity data suggest 

that ammonia toxicity, when expressed in terms of unionized ammonia, does not decrease, and 

possibly even increases, with increasing temperature. Quantifying and adjusting data for this 

relationship is not necessary because even at warm temperatures invertebrates are generally more 

resistant to acute ammonia toxicity than fishes and thus their precise sensitivities are of limited 

importance to the criterion. At low temperatures, they are even more resistant relative to fishes 

and thus their precise sensitivity is even less important to the criterion.

Based on this information, the two issues raised above were resolved as follows:

1. TCAPs will not be used in the ammonia criterion. This does not mean that the notion of 

high temperature exacerbating ammonia toxicity is wrong; rather, it reflects the fact that 

such an effect is not evident in the available data, which cover a wide temperature range.

2. A CMC, if it were expressed as unionized ammonia (rather than total ammonia, used in 

this document) would continue to be lower at lower temperatures, consistent with the 

observed temperature dependence of ammonia toxicity to the most sensitive species, i.e., 

fishes. Although it is possible that the temperature relationship differs among fish species 

and that using the same relationship for all fish species introduces some uncertainty, 

specifying a relationship for each fish species is not possible with current data and would 

also introduce considerable uncertainty.

Therefore, for a criterion expressed in terms of unionized ammonia, available data 

support the continued use of a generic temperature relationship similar to that in the 1984/1985 

ammonia criteria document, but without TCAPs.
205

Figure M.2. The Effect of Temperature on Acute Ammonia Toxicity in Terms of Total Ammonia Nitrogen.

Symbols denote LC50s, solid lines denote regressions for individual datasets, and dotted lines denote pooled regressions over all 

datasets.

0 10 20 30

6

8

15

20

30

40

10

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8

15

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60

10

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100

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100

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4

6

8

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30

10

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6

8

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40

10

0 10 20 30 TOTAL AMMONIA LC50 (mg N/L)

6

8

15

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30

40

10

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15

20

30

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15

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TEMPERATURE (C)

0 10 20 30

40

60

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150

200

300

100

0 10 20 30

40

60

80

150

200

300

100

0 10 20 30

60

80

150

200

300

400

100

Fathead Minnow

(Thurston et al. 1983)

Rainbow Trout

(Thurston and Russo 1983)

Channel Catfish

(Cary 1976)

Channel Catfish

(Colt & Tchobanoglous 1976)

Rainbow Trout

(Ministry of Tech 1968)

Bluegill

(Roseboom & Richey 1977)

Channel Catfish

(Roseboom & Richey 1977)

Largemouth Bass

(Roseboom & Richey 1977)

Rainbow Trout

(Reinbold & Pescitelli 1982a)

Bluegill

(Reinbold & Pescitelli 1982a)

Fathead Minnow

(Reinbold & Pescitelli 1982a)

Striped Bass

(Hazel et al. 1971)

Three-Spined Stickleback

(Hazel et al. 1971)

Fathead Minnow

(DeGraeve et al. 1987)

Channel Catfish

(DeGraeve et al. 1987)

0 10 20 30

80

150

200

300

400

600

100

Atlantic Salmon

(Knopf 1992)

Johnny Darter

(Nimmo et al. 1989)

Fathead Minnow

(Nimmo et al. 1989)
206

Figure M.3. The Effect of Temperature on pH-Adjusted Acute Ammonia Toxicity in Terms of Total Ammonia Nitrogen.

LC50s are adjusted to the mean pH of the dataset based on the pooled relationship of acute toxicity to pH. Symbols denote LC50s, solid 

lines denote regressions for individual datasets, and dotted lines denote pooled regression over all datasets

0 10 20 30

8

15

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30

40

60

10

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6

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8

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0 10 20 30 TOTAL AMMONIA LC50 (mg N/L)

6

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10

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TEMPERATURE (C)

0 10 20 30

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0 10 20 30

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Fathead Minnow

(Thurston et al. 1983)

Rainbow Trout

(Thurston and Russo 1983)

Channel Catfish

(Cary 1976)

Channel Catfish

(Colt & Tchobanoglous 1976)

Rainbow Trout

(Ministry of Tech 1968)

Bluegill

(Roseboom & Richey 1977)

Channel Catfish

(Roseboom & Richey 1977)

Largemouth Bass

(Roseboom & Richey 1977)

Rainbow Trout

(Reinbold & Pescitelli 1982a)

Bluegill

(Reinbold & Pescitelli 1982a)

Fathead Minnow

(Reinbold & Pescitelli 1982a)

Striped Bass

(Hazel et al. 1971)

Three-Spined Stickleback

(Hazel et al. 1971)

Fathead Minnow

(DeGraeve et al. 1987)

Channel Catfish

(DeGraeve et al. 1987)

0 10 20 30

80

150

200

300

400

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100

Atlantic Salmon

(Knopf 1992)

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30

40

10

Johnny Darter

(Nimmo et al. 1989)

Fathead Minnow

(Nimmo et al. 1989)
207

This raised a new issue, however, because the criterion expressed in terms of total 

ammonia is nearly constant over all tested temperatures, and the small effect of temperature on 

the total ammonia criterion in the 1984/1985 criteria document is largely an artifact of 

conducting regression analyses in terms of unionized ammonia and is not indicative of any 

established, significant trend. It was thought that the expression and implementation of the 

ammonia criterion might have been simplified if temperature were dropped as a modifying 

factor, which might have been possible if ammonia toxicity is expressed in terms of total 

ammonia. Furthermore, permit limits and compliance are usually expressed in terms of total 

ammonia nitrogen, and so expressing the criterion in terms of total ammonia nitrogen would 

simplify its implementation by eliminating conversions to and from unionized ammonia. 

Because of such benefits and because there are no compelling scientific or practical reasons for 

expressing the criterion in terms of unionized ammonia, the freshwater toxicity data concerning 

temperature dependence were reanalyzed in terms of total ammonia nitrogen.

The data analyzed are from the studies included in the 1984/1985 ammonia criteria 

document and the studies of DeGraeve et al. (1987), Nimmo et al. (1989), and Knoph (1992). 

All analyses were conducted in terms of total ammonia nitrogen, either as reported by the authors 

or as converted by us from reported values for unionized ammonia, pH, and temperature using 

the speciation relationship of Emerson et al. (1975). The data are presented in Figure M.2 and 

show considerable diversity, with some datasets showing decreasing toxicity with increasing 

temperature, some showing increasing toxicity, and some showing virtually no change. There 

are even differences among studies using the same test species. However, in no case is the effect 

of temperature particularly large, being no more than a factor of 1.5 over the range of any 

dataset, except for the Johnny darter data of Nimmo et al. (1989). In some studies, test pH was 

correlated with test temperature. To reduce the confounding effect of pH, the total ammonia 

LC50 was adjusted to the mean pH of the data for the study using the pH relationship discussed in 

the next section of this appendix. These adjusted data are shown in Figure M.3 and also show 

neither large effects nor any clear consistency among or within species or studies. 
208

For each dataset containing at least three data points, a linear regression of log LC50

versus temperature was conducted (Draper and Smith 1981) and the resulting regression lines are 

plotted as solid lines in Figures M.2 and M.3. These regressions are significant at the 0.05 level 

for only one dataset (the unadjusted fathead minnow data of Thurston et al. 1983); for this 

dataset, however, the regression is not significant when the data are adjusted for the fact that pH

values were lower in the low-temperature tests than in the high-temperature tests. Slopes from 

regression analyses of datasets in Figure M.3 range from -0.015 to 0.013, compared to a range 

from 0.015 to 0.054 when expressed in terms of unionized ammonia (Erickson 1985). This 

narrower range of slopes in terms of total ammonia nitrogen also argues for use of total 

ammonia, rather than unionized ammonia, because there is less uncertainty associated with the 

generic relationship. For datasets with just two points, Figures M.2 and M.3 also show the 

slopes for comparative purposes. Based on the typical uncertainty of LC50s, these slopes also 

would not be expected to be significant, except perhaps for the Johnny darter data of Nimmo et 

al. (1989).

A multiple least-squares linear regression (Draper and Smith 1981) using all datasets 

(with a common slope for all datasets and separate intercept for each dataset) was conducted, 

both with and without pH adjustment. The results of these pooled analyses are plotted as dotted 

lines in Figures M.2 and M.3 to show that the residual errors for the common regression line 

compared to the individual regression lines are not large relative to the typical uncertainty of 

LC50s. To better show the overall fit of the common regression line, the data are also plotted 

together in Figure M.4 by dividing each point by the regression estimate of the LC50 at 20°C for 

its dataset. This normalization is done strictly for data display purposes because it allows all of 

the datasets to be overlaid without changing their temperature dependence, so that the overall 

scatter around the common regression line can be better examined. The data show no obvious 

trend, with the best-fit slope explaining only 1% of the sum of squares around the means for the 

pH-adjusted data and 0% for the unadjusted data. The one available chronic dataset (DeGraeve 

et al. 1987) also shows no significant temperature effect when expressed in terms of total 
209

ammonia nitrogen (Figure M.5) and adjusted for pH differences among the tests. (These tests 

and the calculation of the LC20s are discussed in detail later.)

Based on the small magnitude and the variability of the effect of temperature on total 

ammonia acute and chronic toxicity values for fish, the 1998 Update did not include temperature 

as a modifying factor for a total ammonia criterion. For invertebrates, it should be noted that the 

1998 Update’s assumption that temperature had no effect on the toxicity of total ammonia differs 

from the 1984/1985 criteria document’s assumption that temperature has no effect on the toxicity 

of unionized ammonia. This inconsistency is resolved during the 1999 re-examination of data, to 

be discussed shortly, by incorporating a relationship between temperature and total ammonia 

toxicity to invertebrates. That relationship, however, does not affect the (1999 update) CMC 

because invertebrates are not among the acutely sensitive taxa. 
210

Figure M.4. The Effect of Temperature on Normalized Acute Ammonia Toxicity in Terms of Total Ammonia Nitrogen.

Data were normalized by dividing measured LC50s by regression estimates of LC50s at 20°C for individual datasets for Figure M.2 

(top plot) and Figure M.3 (bottom plot).

0 5 10 15 20 25 30

0.4

0.6

0.8

1.5

2

3

1

ChannelCatfish

Rainbow Trout

Bluegill

ChannelCatfish

LargemouthBass

Rainbow Trout

Bluegill

Fathead Minnow

Striped Bass

Stickleback

Fathead Minnow

ChannelCatfish

AtlanticSalmon

Johnny Darter

Fathead Minnow

TEMPERATURE (C)

0 5 10 15 20 25 30 NORMALIZED TOTAL AMMONIA LC50

0.4

0.6

0.8

1.5

2

3

1

pH Adjusted

Not pH Adjusted
211

Figure M.5. The Effect of Temperature on Chronic Ammonia Lethality to Fathead Minnows in Terms of Total Ammonia 

Nitrogen (DeGraeve et al. 1987).

Symbols denote LC20s and 95% confidence limits and lines denote linear regressions of log LC versus temperature. Figure on left is 

for estimated LC50s at test pH and figure on right is for LC50s adjusted to pH=7.5 based on pooled relationship of chronic toxicity to 

pH.

Temperature (C)

0 5 10 15 20 25 30 Total Ammonia LC20 (mg N/L)

5

20

50

10

100

Data Not pH Adjusted

Temperature (C)

0 5 10 15 20 25 30

5

20

50

10

100

Data Adjusted to pH 7.5
212

The amount of uncertainty in this approach to the CMC can be demonstrated to be small 

by considering how the criterion would differ if total ammonia toxicity was adjusted based on 

the slopes in various datasets. Because the bulk of the toxicity data used in the derivation of the 

criterion is within a few degrees of 20°C, the temperature relationship used has very little effect 

on the criterion near this temperature, but rather has the greatest effect on the criterion at much 

higher or lower temperatures. If the average slope for the pH-adjusted acute data from Figure 

M.4 is used, the total ammonia CMC at 5°C would be only about 6% higher than at 20°C. The 

smallest and largest slopes from the acute regressions for individual species in Figure M.3 would 

produce a range from 40% lower to 68% higher at 5°C than at 20°C, but this greatly overstates 

the uncertainty because effects on a CMC derived from many datasets should not be near these 

extremes.

1999 Re-examination of Temperature Dependence – Acute Toxicity

The previous section, reproduced with relatively few changes from the 1998 Update, 

included an analysis of available data on the temperature dependence of acute ammonia toxicity 

to fish. These data (in Figures M.2, M.3, and M.4) consisted of 20 different data sets drawn from 

11 different studies and included nine different species, four of these species being in more than 

one study. Data from Arthur et al. (1987) were not used in the 1998 analysis because those 

authors reported concerns about factors confounding temperature in their data set. Linear 

regression analysis of log LC50 (total ammonia basis) versus temperature was conducted on each 

data set, both with and without correcting for pH as a confounding factor. No consistent trend 

with temperature was observed and only one data set showed a slope different than zero at the 

0.05 level of statistical significance. Therefore, a pooled linear regression analysis was 

conducted across all data to derive an average slope, which was very close to zero and also not 

statistically significant. On the basis of this analysis, the 1998 Update did not include any 

temperature dependence for criteria to protect fish from acute ammonia toxicity. 

In response to public comment (U.S. EPA, 1999), the 1998 analysis was re-examined. 

This re-examination indicated that it is appropriate to handle the temperature dependencies of 

fish and invertebrates separately. For invertebrates, the inclusion of the Arthur et al. (1987) data 

in the regression analysis yields a change in the temperature dependency that is ultimately 

reflected in the difference between the 1999 CCC and the 1998 CCC. 
213

In the 1998 Update, EPA did not use the Arthur et al. (1987) data because of those 

authors concerns that other variable factors in their tests, conducted during different seasons, 

might have had a potential to confound their results. In re-examining their data in response to 

comments, however, EPA found that most of the fish data from Arthur et al. showed behavior 

similar to that from numerous other investigators: that is, little relationship with temperature 

when expressed as total ammonia. Consequently, it was concluded that the other variable factors 

were unlikely to be confounding the results.

For fish, although the temperature dependency is unchanged from 1998, additional 

documentation is provided here, primarily because the apparent difference between fish acute 

and chronic temperature dependencies is now used in the projection of the invertebrate chronic 

temperature dependency. 

First presented here will be more details on the regression analyses of the individual data 

sets conducted for the Update, plus similar analyses of the data of Arthur et al. A linear 

regression was conducted on each data set using the equation:

log(LC50T) = log(LC5020) + S (T- 20)

where LC50T is the total ammonia LC50 at temperature T, S is the slope of log LC50 versus 

temperature, and LC5020 is the estimated total ammonia LC50 at 20°C. For completeness, this 

effort included data sets with just two points, although the regression analysis then provides a 

perfect fit and has no residual error, so that confidence limits, significance levels, etc. cannot be 

evaluated using normal methods. In such cases, the mean squared error (MSE) of data around 

the regression was assumed to be equal to the weighted mean residual MSE for the larger data 

sets, so that approximate significance levels could be determined.

Fish acute data:

Table M.1 presents the results of the regression analysis for each data set, with data 

adjusted to pH=8 based on the average pH relationship used in the 1998 and 1999 Updates. 

Plots of these relationships (except for Arthur et al. 1987) are in Figure M.3 in the previous 

section.
214

Of the 24 entries in Table M.1, nearly half (11) have very small slopes of between -0.006 

and +0.006, a range which corresponds to a factor of 1.3 change or less in LC50 for a 20°C 

temperature change and is less than normal data variability. Of these 11, five have positive 

slopes and six have negative slopes. Of the 13 entries with steeper slopes, five have positive 

slopes and eight have negative slopes. Among the data sets used in the Update, only two of the 

regressions are statistically significant at the 0.05 level, one with a negative slope and one with a 

positive slope, although two other sets (for fathead minnows from DeGraeve et al. 1987 and 

Reinbold and Pescitelli 1982b) are close to being significant. (The level of significance for the 

Johnny darter data set differs from what was reported in the previous section because it consists 

of two different sets which were analyzed separately in the 1998 analysis, but combined here 

because they were not significantly different.) Of the five data sets from Arthur et al. (1987), 

only one is significant at the 0.05 level. For species with more than one entry, slopes vary 

considerably. This general lack of statistical significance and consistency precludes any reliable 

assessments based on these individual analyses. 

The 1998 Update therefore conducted a pooled regression analysis to determine whether 

the combined acute toxicity data sets indicated any significant average trends with temperature. 

Table M.2 summarizes the mean trends determined in various pooled analyses. The first entry is 

the pooled analysis conducted for the 1998 Update, which included all the data in Table M.1 

above except the fish data of Arthur et al. (1987). The slope from this pooled analysis was very 

small (-0.0023), and was not statistically significant despite the large number of data. The 

second entry adds the fish data of Arthur et al.; it does result in a statistically significant trend. 

The mean slope (-0.0058) is still small, but does amount to a 23% decrease in LC50 per 20°C 

increase in temperature. However, this slope is heavily influenced by two points with high 

residual (>3σ) deviations. One of these points is a test at 3.4°C by Arthur et al. (1987) with 

fathead minnows, which showed much greater effects of low temperature than other studies with 

the same species. The other point is for a test at 22.6°C by Arthur et al. (1987) with walleye, 

which showed very high sensitivity and was part of a set of three tests which used fish from 

different sources, potentially confounding the temperature effects. Without these two data, the 

regression has an even lower slope and is not significant at the 0.05 level (third entry in Table 

M.2). Overall, these analyses of the fish acute data suggest a weak overall trend of higher LC50s 
215

at low temperatures, with a logLC50 versus temperature slope in the -0.002 to -0.006 range, but 

of questionable statistical significance.

Table M.1. Results of Regression Analysis of logLC50 (mg/L total ammonia nitrogen) 

Versus Temperature (°C) for Individual Data Sets on the Temperature Dependence of 

Acute Ammonia Toxicity.

Table M.1

Reference/

Species

Slope

(95% CL)

logLC5020

(95% CL)

Residual SD

(r2)

FREGR

(α)

Thurston et al. (1983)

Fathead Minnow

-0.0014

(-0.013,+0.013)

1.641

(1.582,1.700)

0.112

(<1%)

0.06

(0.81)

Thurston and Russo (1983)

Rainbow Trout

+0.0059

(-0.017,+0.029)

1.350

(1.204,1.495)

0.121

(2%)

0.30

(0.59)

Cary (1976)

Channel Catfish

+0.0028

(-0.008,+0.013)

1.676

(1.593,1.758)

0.093

(2%)

0.32

(0.58)

Colt and Tchobanoglous (1976)

Channel Catfish

+0.0004

(-0.037,+0.038)

1.604

(1.350,1.858)

0.016

(2%)

0.02

(0.91)

Ministry of Technology (1967)

Rainbow Trout

+0.0008

(-0.018,+0.019)

1.231

(1.010,1.452)

0.051

(1%)

0.03

(0.88)

Roseboom and Richey (1977)

Bluegill Sunfish

+0.024

(-0.025,+0.073)

1.089

(0.803,1.375)

- 0.95

(0.33)

Roseboom and Richey (1977)

Channel Catfish

+0.020

(-0.029,+0.069)

1.482

(1.196,1.768)

- 0.68

(0.41)

Roseboom and Richey (1977)

Largemouth Bass

-0.0029

(-0.040,+0.034)

1.237

(0.972,1.502)

- 0.02

(0.88)

Reinbold and Pescitelli (1982b)

Rainbow Trout

-0.0088

(-0.028,+0.010)

1.396

(1.159,1.632)

0.088

(29%)

1.63

(0.27)

Reinbold and Pescitelli (1982b)

Bluegill Sunfish

-0.0004

(-0.027,+0.026)

1.370

(1.059,1.681)

0.128

(0%)

0.00

(0.96)

Reinbold and Pescitelli (1982b)

Fathead Minnow

-0.0153

(-0.031,+0.009)

1.429

(1.243,1.615)

0.076

(89%)

16.6

(0.06)

Hazel et al. (1971)

Striped Bass

-0.0163

(-0.057,+0.025)

1.274

(1.105,1.443)

0.076

(60%)

2.93

(0.23)

Hazel et al. (1971)

Three-Spined Stickleback

-0.0106

(-0.053,+0.032)

1.390

(1.214,1.567)

0.081

(36%)

1.14

(0.40)

DeGraeve et al. (1987)

Fathead Minnow

-0.0052

(-0.012,+0.002)

1.617

(1.563,1.670)

0.061

(36%)

3.33

(0.12)

DeGraeve et al. (1987)

Channel Catfish

-0.0088

(-0.016,-0.002)

1.648

(1.595,1.701)

0.061

(62%)

9.76

(0.02)

Knopf (1992)

Atlantic Salmon

-0.0035

(-0.027,+0.020)

1.715

(1.406,2.025)

0.097

(7%)

0.22

(0.067)

Knopf (1992)

Atlantic Salmon

+0.0163

(-0.075,+0.108)

1.636

(0.405,2.866)

0.054

(84%)

5.18

(0.26)

Nimmo et al. (1989)

Johnny Darter

+0.021

(+0.000,+0.043)

1.463

(1.248,1.678)

0.072

(90%)

18.1

(0.05)

Nimmo et al. (1989)

Fathead Minnow

+0.0070

(-0.014,+0.028)

1.568

(1.353,1.782)

- 0.42

(0.52)

Arthur et al. (1987)

Fathead Minnow

-0.032

(-0.059,-0.004)

1.762

(1.493,2.030)

0.105

(92%)

24.8

(0.04)
216

Table M.1

Reference/

Species

Slope

(95% CL)

logLC5020

(95% CL)

Residual SD

(r2)

FREGR

(α)

Arthur et al. (1987)

Rainbow Trout

-0.0100

(-0.053,+0.033)

1.348

(0.937,1.758)

0.158

(16%)

0.56

(0.51)

Arthur et al. (1987)

Channel Catfish

-0.0058

(-0.038,+0.027)

1.558

(1.230,1.886)

0.030

(84%)

5.15

(0.26)

Arthur et al. (1987)

White Sucker

+0.0007

(-0.23,+0.25)

1.902

(1.657,2.147)

0.048

(1%)

0.01

(0.92)

Arthur et al. (1987)

Walleye

-0.038

(-0.327,+0.250)

1.216

(-1.911,4.343)

0.306

(74%)

2.84

(0.34)

Table M.2. Results of Regression Analysis of log LC50 (mg/L total ammonia nitrogen) 

Versus Temperature (°C) for Pooled Data Sets on the Temperature Dependence of Acute 

Ammonia Toxicity to Fish.

Data Sets Pooled Slope

(95% CL)

Residual SD

(r2)

FREGR

(α)

All Data excluding Arthur et al. -0.0023

(-0.0057,+0.0011)

0.105

(2%)

1.79

(0.18)

All Data including Arthur et al. -0.0058

(-0.0094,-0.0022)

0.122

(8%)

10.3

(<0.01)

All Data including Arthur et al. except "Outliers" -0.0030

(-0.0063,+0.0002))

0.105

(3%)

3.52

(0.06)

Fathead Minnow excluding Arthur et al -0.0063

(-0.0122,-0.0005)

0.106

(11%)

4.76

(0.04)

Fathead Minnow including Arthur et al. -0.0105

(-0.0169,-0.0049)

0.120

(25%)

13.4

(<0.01)

Fathead Minnow including Arthur et al. excl "Outlier" -0.0073

(-0.0129,-0.0017)

0.106

(15%)

6.85

(0.01)

Rainbow Trout excluding Arthur et al. -0.0013

(0.0122,+0.0096)

0.109

(<1%)

0.06

(0.80)

Rainbow Trout including Arthur et al. -0.0034

(-0.0133,+0.0064)

0.115

(2%)

0.51

(0.48)

Channel Catfish excluding Arthur et al. -0.0030

(-0.0091,+0.0031)

0.088

(4%)

1.05

(0.32)

Channel Catfish including Arthur et al. -0.0034

(-0.088,+0.021)

0.085

(6%)

1.64

0.21)

Bluegill Sunfish +0.0006

(-0.0172,+0.0184)

0.120

(<1%)

0.01

(0.92)
217

It is also useful to consider separately the overall trends for different fish species. Table 

M.1 includes multiple studies with fathead minnows, rainbow trout, channel catfish, and bluegill 

sunfish. Table M.2 includes the results of pooled analyses for each of these species, both with 

and without data from Arthur et al. (1987). For rainbow trout, bluegill, and channel catfish, the 

regressions were not statistically significant. The bluegill data indicated virtually no temperature 

effect, whereas weak trends similar to the pooled analyses over all data sets were suggested in 

the channel catfish data (slope = -0.0030 without and -0.0034 with Arthur et al. data) and 

rainbow trout data (slope = -0.0014 without and -0.0034 with Arthur et al. data). For fathead 

minnow, the pooled analyses were statistically significant and stronger, with slopes ranging from 

-0.0063 to -0.0105 depending on the treatment of data from Arthur et al. Such slopes for fathead 

minnow would result in moderate effects over a broad temperature range: a 20°C decrease in 

temperature would result in a 33% to 62% increase in LC50. However, this species is not 

sensitive enough that this would affect the acute criterion values. For the species used in the 

acute criterion calculations, no temperature correction for acute toxicity is appropriate due to the 

lack of any significant trend over all data sets.

Invertebrate acute data:

Unlike fish, available acute toxicity data for invertebrates indicates that their acute 

sensitivity to ammonia decreases substantially with decreasing temperature. The 1998 Update 

noted this temperature dependence, but did not present any analysis of it because tested 

invertebrates were sufficiently tolerant to acute ammonia exposures that this dependence would 

not affect the acute ammonia criterion. The 1998 Update also noted that this temperature 

dependence should be a consideration in setting low temperature chronic criterion, but did not 

provide any specific analysis regarding this. This section will provide an analysis of available 

information on the temperature-dependence of invertebrate acute ammonia toxicity, to be used 

later for estimating the temperature-dependence of chronic ammonia toxicity.

Arthur et al. (1987) provide the only available data on the temperature dependence of 

acute ammonia toxicity to invertebrates. As noted earlier, these toxicity tests did not specifically 

test temperature effects, but rather were seasonal tests in which various chemical characteristics 

of the tests water varied as well as temperature. Test organisms were whatever were available in 

outdoor experimental streams at the time of the test, so the size, life stage, and condition of the 
218

organisms also varied. The authors of this study expressed some doubt as to how much of the 

effects they observed were actually due to temperature. However, for invertebrates, they did 

observe strong correlations of total ammonia toxicity with temperature. Confounding factors 

might contribute somewhat to this correlation, but temperature is still likely the primary 

underlying cause. If other factors were largely responsible for the apparent effects of 

temperature, it would be expected that strong correlations with temperature would also be 

evident in their fish data. However, as discussed above, the fish data usually showed much 

weaker effects of temperature, similar to other studies with fewer confounding factors.

These invertebrate acute data were analyzed using the same regression model and 

techniques as discussed above for fish. The study of Arthur et al. (1987) included data sets for 

nine invertebrate species, but two of these sets were not included in the analysis because they 

consisted of two tests at temperatures only 3°C apart. For the other species, the number of tests 

ranged from 2 to 6, with temperature ranges of from 9°C to 21°C. Table M.1 summarizes the 

regression results for the data sets of each species and for pooled analyses conducted on (a) all 

seven species, and (b) three species that had more than two tests and a temperature range of at 

least 15°C. All data were corrected to pH 8 based on the average acute pH relationship 

(described later). All species show substantially greater tolerance to ammonia at lower 

temperatures, and in most cases the significance level of the regression is better than 0.05. (As 

for the analysis of the fish data, when there were just two tests for a species, the significance 

level for the individual analysis is based on the MSE from the pooled analysis.) The slope of log 

LC50 versus temperature does not vary widely, ranging from -0.028 to -0.046 and being -0.036 

for both pooled analyses. Figure M.6 provides plots of this data and the regression lines 

comparable to those for fish previously shown in Figures M.3 and M.4.

Again, because invertebrates are not among the species acutely sensitive to ammonia (in 

the 1999 update), the invertebrate acute temperature slope does not affect the formulation of the 

acute criterion. It will be used subsequently, however, in formulating the invertebrate chronic

temperature slope, which ultimately will affect the formulation of the chronic criterion.
219

1999 Re-examination of Temperature Dependence – Chronic Toxicity

Fish chronic data

As in the 1998 Update, the only available data on the temperature dependence of chronic 

ammonia toxicity are from the study by DeGraeve et al. (1987) on survival of juvenile fathead 

minnows during 30-day exposures to ammonia at temperatures ranging from 6°C to 30°C. In 

contrast to acute toxicity, which for fathead minnows showed sensitivity to be slightly reduced at 

low temperatures, this data on chronic toxicity suggested greater sensitivity at low temperatures. 

However, this trend was small, at least once the confounding effect of pH was corrected for, and 

not statistically significant. Based on this analysis, the 1998 Update treated effect concentrations 

for chronic ammonia toxicity to fish as it did for acute toxicity: as being invariant with 

temperature. However, the 1998 Update also noted that, if seasonal variations in temperature 

cause a shift in what endpoints the criterion should be based on, the chronic criterion could have 

a seasonal temperature dependence even if effect concentrations for specific chronic endpoints 

do not vary with temperature (This is discussed in the 1999 AQWC document under the section 

named Seasonality of Chronic Toxicity Endpoints).

This section will provide more details regarding the analysis of the chronic toxicity data 

from DeGraeve et al. (1987), and a comparison of its temperature dependence to that of acute 

toxicity in the same study. Figure M.5 showed the temperature dependence of acute and chronic 

effect concentrations from this study.

An important issue in this analysis is the confounding effect of pH on the apparent effect 

of temperature, because pH increased with decreasing temperature in these chronic exposures. 

To examine what the effect of temperature is, the effect concentrations should be adjusted to a 

common pH using an equation that accounts for the effect of pH. A critical question then is what 

pH equation to use, because no study exists for the effect of pH on this particular chronic 

endpoint (juvenile 30-day survival), or on the interaction of pH and temperature effects. The 

1998 Update used the pH relationship derived for the chronic criterion. Of the pH relationships 

available, that one is probably most appropriate, but entails some uncertainty. To evaluate how 

conclusions about temperature effects will vary if the true pH relationship is different, this 

analysis will also use the pH relationship for acute toxicity to fathead minnows from Thurston et 

al. (1983). This relationship likely represents an extreme possibility; i.e., it assumes that chronic 
220

toxicity pH relationships are the same acute ones, contrary to what is indicated by available 

chronic studies.
221

Figure M.6. Temperature Dependence of Acute Ammonia Toxicity to Invertebrate 

Organisms from Arthur et al. (1987).

0 10 20 30

20

50

200

500

100

Physa gyrina

0 10 20 30

50

200

500

100

1000

Physa gyrina

(Arthur et al. 1987)

0 10 20 30

20

50

200

10

100

Physa gyrina

(Arthur et al. 1987)

Temperature Dependence of Acute Ammonia Toxicity 

to Invertebrate Organisms from Arthur et al. (1987).

(Solid line denotes species slope; Dotted line denotes pooled slope)

0 10 20 30

20

50

200

500

100

0 10 20 30

200

500

2000

5000

1000

Crangonyx pseudogracilis

0 10 20 30

NORMALIZED TOTAL AMMONIA LC50 (mg N/L Total Ammonia at pH=8) 20

50

200

500

100

Musculium transversum

0 10 20 30

200

500

2000

100

1000

Orconectes immunis

Helisoma trivolvis Asellus recovitzai Philarctus quaeris

TEMPERATURE (C)

0 10 20 30 Observed LC50/Estimated LC50 @ 20 C 0.5

2

5

1

10

All Species

0 10 20 30

0.5

2

5

1

10

Physa,Crangonyx, Musculium Observed LC50/Estimated LC50 @ 20 C
222

Using the pooled chronic pH relationship (presented later in this document), slope=0.010, 

significance=0.13, and r2=0.76. Using the fathead minnow acute pH relationship, slope=0.0053, 

significance=0.32, and r2=0.45. In neither case is the regression statistically significant at the 5 

percent level, due to the amount and variability of the data. Nevertheless, it should be noted that, 

in both cases, the chronic data show an upward trend with temperature, in contrast to that 

observed for acute toxicity. Even under the extreme assumption that these data have a pH 

relationship similar to acute toxicity, the slope is 0.005, and is twice this under the assumption 

that these data follow the chronic pH relationship. Thus, even if fathead minnows show 

increased acute tolerance to ammonia at low temperatures, a similar assumption for chronic

toxicity is contraindicated.

The difference between acute and chronic temperature relationships can be better 

assessed by looking at acute-chronic ratios. Figure M.7 shows the temperature dependence of 

the ratio of the acute LC50 to the chronic LC20. The chronic LC20s used for the ACRs were 

normalized via the above two alternative pH relationships, while the acute LC50s were 

normalized only using the acute pH relationship. The results show that for either pH 

normalization alternative, the ACRs are substantially higher at lower temperatures than at higher 

temperatures. If the chronic data are pH-normalized using the chronic pH relationship, the 

regression is significant at the 0.05 level, with a slope of -0.0155. If normalized using the acute 

pH relationship, the slope is less (-0.0110), but even with this extreme assumption, there is only a 

13 percent probability that the regression slope arose by chance.

It is not surprising that acute-chronic ratios are higher at low temperature. Temperature 

can affect toxicity in a variety of ways, one of which is simply to slow down responses. This is 

evident in some reports on the effect of temperature on ammonia toxicity. For example, for the 

rainbow trout data from Ministry of Technology (1967), there was little effect of temperature on 

total ammonia LC50s at 96 hours, but at shorter durations LC50s increased with decreasing 

temperature. The overall impact on the temperature dependence of LC50s and ACRs will depend 

on the duration of the acute toxicity test and on the speed of action of acute ammonia toxicity in 

the species of concern. However, temperature is likely to affect ammonia toxicity in multiple 

ways, some of which would alter acute and chronic toxicity similarly. Nonetheless, to some 

degree the ratio of effect concentrations at different durations is expected to increase at lower 
223

temperatures. This expectation, as well as the empirical evidence, argues against the direct 

application of acute temperature relationships to chronic toxicity.

Figure M.7. Temperature-Dependence of Ammonia ACRs for Fathead Minnows.

(The choice of reference condition, pH=8 here versus pH=7.5 in Figure M.5, has no effect on 

slope or significance.)

Temperature (C)

0 5 10 15 20 25 30 Ratio of 96-hour LC50 to 30-day LC20

2

3

4

5

7

1

10

Chronic Data Adjusted to pH=8

Using Update Average

Chronic pH Relationship

Temperature (C)

0 5 10 15 20 25 30

2

3

4

5

7

1

10

Chronic Data Adjusted to pH=8

Using Fathead Minnow

Acute pH Relationship

Slope = -0.0155

r

2 = 90%

Siglevel = 0.05

Slope = -0.0111

r

2

 = 80%

Siglevel = 0.11

Figure 1. Temperature Dependence of Acute Ammonia Toxicity 

to Invertebrate Organisms from Arthur et al. (1987).

(Solid line denotes species slope; Dotted line denotes pooled slope)

Temperature-dependence of ammonia acute:chronic ratios for fathead minnows 

Invertebrate chronic projections

No data are available on the effect of temperature on chronic ammonia toxicity to 

invertebrates. Because invertebrates are much more acutely tolerant at low temperatures than at 

high temperatures, it is likely that their chronic toxicity would also show some temperature 

dependence. However, as discussed above, there is reason to expect acute and chronic toxicity to 

vary somewhat differently with temperature, with acute-chronic ratios increasing at low 

temperature, especially for organisms for which acute ammonia toxicity is not especially fast, 

which is the case for invertebrates (Thurston et al. 1984b). The observed trend in the fathead 

minnow ACRs provides support for this expectation.

The critical question then becomes, how much of the acute temperature slope for 

invertebrates should be assumed to apply to chronic toxicity? If this slope is predominantly due 
224

to temperature-induced delays of acute toxicity, chronic toxicity might have very little slope. If 

this slope is not at all due to such delays, then all the slope should be applied to chronic toxicity.

One option for an objective mathematical prediction of the invertebrate chronic slope is 

to assume that the difference between acute and chronic slopes will be the same for fish and 

invertebrates, potentially implying that the effect of temperature on the kinetics of toxicity is 

roughly the same for fish and invertebrates. In this case the invertebrate chronic slope would be 

the difference between -0.036, the average invertebrate acute slope, and -0.016, the observed 

slope for fish acute-chronic ratios. This would yield an invertebrate chronic slope of -0.020. 

This correction still applies most of the acute slope to chronic toxicity, but recognizes that the 

chronic slope should probably be less steep.

It is recognized that few data are available to define the Figure M.7 fish ACR slope, and 

that the assumption the invertebrate ACR slope would equal the fish ACR slope is quite 

uncertain despite having some theoretical underpinning in the kinetics of toxicity. Consequently 

a second option is to equate the invertebrate chronic slope to the invertebrate acute slope (-0.036) 

minus one-half the fish ACR slope (-0.016/2). This splits the difference between no correction 

and full correction for the fish ACR slope, resulting in an invertebrate chronic slope of -0.028.

A third, related option is suggested from the appearance of data in the last two plots in 

Figure M.6, plots of “All Species” and “Physa, Crangonyx, Musculium”. These plots suggest a 

steeper invertebrate acute slope at higher temperatures than at very low temperature. At greater 

than 10°C, these data also comfortably fit a slope of -0.044. If such a slope were used to fit those 

data, however, a concentration plateau would need to be imposed between 5 and 10°C to avoid 

over-estimating the acute effect concentrations measured near 5°C. If the invertebrate chronic 

slope is obtained by subtracting the full value of the fish ACR slope (-0.016), this would yield 

the same invertebrate chronic slope, -0.028, as the option in the previous paragraph. In this case, 

however, concentrations would be capped between 5 and 10°C in order to reflect the implied 

attenuation of slope at low temperature relative to higher temperatures.

EPA selected this third option, a compromise between the first two options, for defining 

the invertebrate chronic temperature slope in formulating the CCC, discussed later. This 

provides a good fit to the available information.
225

Appendix N. Site-Specific Criteria for Ammonia.

Recalculation Procedure for Site-specific Criteria Derivation

The water quality standards (WQS) regulation at 40 CFR § 131.11(b)(1)(ii) provides

states with the opportunity to adopt water quality criteria that are “...modified to reflect sitespecific conditions.” As with any criteria, site-specific criteria must be based on a sound 

scientific rationale in order to protect the designated use and are subject to review and approval

or disapproval by EPA.

The recalculation procedure for site-specific criteria derivation is intended to allow sitespecific criteria that differ from national criteria recommendations (i.e., concentrations that are 

higher or lower than national recommendations) where there are demonstrated differences in 

sensitivity between the aquatic species that occur at the site and those that were used to derive 

the national criteria recommendations. The national dataset may contain aquatic species that are 

sensitive to a particular pollutant, but these or comparably sensitive species might not occur at 

the site (e.g., freshwater mussels are included in the national ammonia dataset but may not be 

present at a particular site). On the other hand, a species that is critical at the site might be 

sensitive to the pollutant and require site-specific criteria that are lower than the national 

recommended criteria.

In the case of ammonia, where a state demonstrates that mussels are not present on a sitespecific basis, the recalculation procedure may be used to remove the mussel species from the 

national criteria dataset to better represent the species present at the site. For example, many of 

the commonly occurring freshwater bivalves (e.g., pea clam) are more closely related to the nonunionid fingernail clam Musculium (which is the fourth most sensitive genus in the national 

dataset for the chronic criterion) than to the unionid mussels Lampsilis and Villosa (which are the 

two most sensitive genera in the national dataset for the chronic criterion). At sites where all 

bivalves present are more closely related to Musculium than to Lampsilis and Villosa (i.e., where 

unionid mussels are not present at the site), the recalculation procedure may be used to remove 

Lampsilis and Villosa from the dataset because they would not be representative of the species 

present at the site. With removal of Lampsilis and Villosa from the national dataset, the 

recalculation procedure could result in criteria (and associated water quality-based effluent limits 

(WQBELs) based on such criteria) with higher concentrations than EPA’s recommendations but 
226

that are still protective of the designated use. The retention of Musculium in the dataset would 

represent the other non-unionid bivalves present at the site, so the non-unionid bivalves would 

still be protected if Lampsilis and Villosa were removed from the chronic dataset. However, at 

sites where both unionid and non-unionid bivalves are present, all three bivalves in the national 

chronic dataset (i.e., Lampsilis, Villosa, and Musculium) would be retained because they would 

represent the species present at the site. The recalculation procedure describes how to compare 

the taxonomy of species present at the site with the taxonomy of species in the national dataset. 

The number of tested genera (N) in the criteria calculations must be updated where 

genera such as Lampsilis and Villosa are removed from the dataset. For example, if only the two 

unionid mussels are removed from the dataset for the national chronic ammonia criterion, N 

would be reduced from 16 genera in the national dataset to 14 genera in the site-specific dataset, 

and this would affect the site-specific criteria values.

Freshwater snails represent another sensitive freshwater species group for which acute 

and chronic toxicity data exist and are used in criteria derivation. Because freshwater snails tend 

to be more ubiquitous in the environment, however, the existing data for these animals are not 

likely to be deleted from the datasets in a criteria recalculation.

As with any criteria, states choosing to utilize the recalculation procedure should ensure 

that their site-specific criteria “...provide for the attainment and maintenance of the water quality 

standards of downstream waters.” 40 CFR § 131.10(b). In addition, states should consider how 

they will demonstrate that mussels are not present at the site before selecting this approach. For 

additional information on the recalculation procedure, see EPA’s Water Quality Standards 

Handbook at http://www.epa.gov/wqshandbook.

Acute Criterion Magnitude Recalculation for Ammonia

Unionid Mussels Present and Oncorhynchus species Absent

Where Oncorhynchus species are absent, EPA does not lower its acute criteria for 

ammonia below the 5th percentile in order to protect the commercially and recreationally 

important adult rainbow trout, but instead, retains all tested species in the Order Salmoniformes 

as tested surrogate species representing untested freshwater fish resident in the U.S. from another 

Order. The lowest GMAV for a freshwater fish (vertebrate species) is 51.93 mg TAN/L for 

Prosopium (Table 3). Therefore, in this case, the CMC equals the lower of: a) 0.7249 times the 
227

temperature adjusted lowest invertebrate GMAV (e.g., 17 mg TAN/L at pH 7.0 and 20o C), or (b)

0.7249 times the lowest freshwater fish GMAV (e.g., 38 mg TAN/L at pH 7.0), according to the 

following temperature relationship:

 ( ( ))

Thus, the CMC increases with decreasing temperature as a result of increased invertebrate 

insensitivity until it reaches a plateau of 37.65 mg TAN/L at 10.2°C and below (51.93 mg 

TAN/L x 0.7249), where the most sensitive taxa switches to the temperature invariant fish genus 

Prosopium (Tables 5b and N.1; see also Oncorhynchus absent line in Figure 5a). Note: while the 

mountain whitefish (Prosopium williamsoni) is a species in the same family as Oncorhynchus sp. 

(i.e., Family: Salmonidae), it is also an appropriately sensitive surrogate species amongst all 

freshwater fish in the Class Actinopterygii. 

The CMC where Oncorhynchus sp. are absent extrapolated across both temperature and 

pH is as follows:

 (

 

 

 

 ) ( ( )

)

When a threatened or endangered species occurs at a site and sufficient data indicate that it is 

sensitive at 1-hour average concentrations below the CMC, it is appropriate to consider deriving 

a site-specific criterion. It should be noted that the dataset used to derive these new ammonia 

criteria included some threatened or endangered species, none of which were the most sensitive 

of the species tested. Extrapolated values across a range of temperatures and pH values are 

presented in Table N.1.

Unionid Mussels Absent and Oncorhynchus spp. Present

If a state can demonstrate that unionid mussels are not present at a site, a site-specific 

criteria can be calculated for waters with mussels absent. It is important to recognize that for 

site-specific criteria derived where unionid mussels are absent, the commercially and 
228

recreationally important adult rainbow trout (Oncorhynchus mykiss) is the most acutely sensitive 

species. Thus, when Oncorhynchus spp. are present, the acute criterion cannot exceed 24 mg 

TAN/L (the SMAV for adult rainbow trout 48.21 mg TAN/L divided by two – see also Acute 

Criterion Calculation section in this document). 

At pH 7, the temperature relationship is expressed as follows:

 ( ( ( )))

Where 24.10 mg TAN/L is one half the SMAV of 48.21 mg TAN/L for adult rainbow trout, and 

45.05 is 0.7249 (the CMC divided by the lowest GMAV in the complete acute dataset) 

multiplied by 62.15 mg TAN/L, the GMAV of the temperature dependent pebblesnail 

(Fluminicola sp.), the most sensitive non-mussel invertebrate (Table N.2).

At temperatures 0 - 27.5°C, the CMC with mussels absent and Oncorhynchus spp.

present is 24.10 mg TAN/L, because adult rainbow trout remain the most sensitive species group 

in this temperature range. At temperatures greater than 27.5°C, however, the GMAV for 

Fluminicola species (62.15 mg TAN/L) becomes the most sensitive GMAV because 

invertebrates are increasingly more acutely-sensitive to ammonia as temperature increases, and 

thus, the CMC equals that of the mussels absent, Oncorhynchus sp. absent temperature 

relationship (Figure N.1). Consistent with the approach followed with the unionid mussels 

present, Oncorhynchus species absent CMC calculation in the Acute Criterion Calculations

section of this document, the site-specific criteria should 1) retains all tested species in the Order 

Salmoniformes as tested surrogate species representing untested freshwater fish resident in the 

U.S. from another Order; and 2) maintains the SSD relationship from the complete acute dataset 

(i.e., CMC is equal to the lowest GMAV times 0.7249). 

The CMC, where mussels are absent and Oncorhynchus spp. are present, extrapolated 

across both temperature and pH is as follows (extrapolated values provided Table N.3):

 ((

 

 

 

 ) ( (

 

 

 

 )

 ( )))
229

Unionid Mussels Absent and Oncorhynchus spp. Absent

If both unionid mussels and Oncorhynchus spp. are absent, the CMC calculated using the 

Guidelines algorithm is 30.25 mg TAN/L at pH 7 and 20°C and is based on the four most 

sensitive GMAVs in the following rank order: mountain whitefish, Lost River sucker, 

pebblesnail, and golden shiner (see Table N.2). The ratio of the mussels absent and 

Oncorhynchus spp. absent CMC to the most sensitive GMAV (i.e., mountain whitefish; 

Prosopium sp.) is 0.5825, or 30.25 mg TAN/L divided by 51.93 mg TAN/L. However, this 

would result in a more protective criterion than when Oncorhynchus spp. are absent but mussels 

are present (see Acute Criterion Calculations). Because the unionid mussels absent and

Oncorhynchus spp. absent CMC cannot be more protective than the unionid mussels present and 

Oncorhynchus spp. absent CMC, the CMC to lowest GMAV ratio of 0.7249 from the complete 

acute dataset is multiplied by 51.93 mg TAN/L for Prosopium sp., the lowest GMAV in the 

unionid mussels absent dataset, resulting in a calculated CMC of 37.65 mg TAN/L at pH 7 and 

20°C. This is equivalent to the maximum plateau CMC when mussels are present and 

Oncorhynchus spp. are absent at temperatures of 10.2°C and below (compare in Figures 5a and 

N.1).

At pH 7, the temperature relationship is expressed as follows:

 ( ( ( )))

At temperatures between 0-22.1°C the CMC with unionid mussels and Oncorhynchus 

spp. absent is 37.65 mg TAN/L. At temperatures greater than 22.1°C, the temperature dependent 

pebblesnail (Fluminicola sp.) becomes the most sensitive GMAV, and the CMC decreases with 

increasing temperature (Figure N.1).

The CMC, where both unionid mussels and Oncorhynchus spp. are absent, extrapolated 

across both temperature and pH is as follows (extrapolated values provided Table N.4):

 (

 

 

 

 ) ( ( ( )

))
230

A summary of the acute criterion recalculations for all four mussel and Salmonid present and 

absent combinations at pH 7 and 20°C is included in Table N.5.

Chronic Criterion Magnitude Recalculation for Ammonia

Unionid Mussels Absent, Early Life Stage (ELS) Protection Necessary

When unionid mussels are present, the CCC is the same regardless of whether early life 

stages (ELS) of fish genera require protection. This is because unionid mussels represent the two 

most sensitive genera in the chronic dataset, and at pH 7, the CCC at the invertebrate temperature 

plateau of 7°C is 4.363 mg TAN/L, which is lower than the GMCV for Lepomis, the most 

sensitive fish genera, multiplied by the CCC to lowest GMCV ratio (or 6.920 mg TAN/L x 

0.8876 = 6.142 mg TAN/L – see Chronic Criterion Calculations for additional details).

When unionid mussels are absent and fish ELS require protection, however, the CCC is 

6.508 mg TAN/L at pH 7 and 20°C (Tables N.6, N.7). The lowest GMCV is 6.920 mg TAN/L 

for the temperature invariant vertebrate genus Lepomis, and the most sensitive invertebrate 

GMCV is 7.547 mg TAN/L for Musculium (Table N.6). The ratio of the CCC to the most 

sensitive GMCV (Lepomis sp.) when unionid mussels are absent is 0.9405, or 6.508 mg TAN/L 

divided by 6.920 mg TAN/L. At pH 7 and 20°C, the CCC when mussels are absent and ELS 

protection is required is expressed as follows:

 ( ( ( )))

This function remains constant at a CCC equal to 6.508 mg TAN/L at 0-21.3°C because 

the most sensitive GMCV is for the temperature invariant genera Lepomis (Figure N.2; Table 

N.6). At temperatures greater than 21.3°C, the GMCV for the invertebrate Musculium (i.e., 

7.547 mg TAN/L) becomes the most sensitive, and the CCC decreases with increasing 

temperature (Figure N.2). 

When unionid mussels are absent and ELS protection is required, the thirty-day average 

concentration of ammonia nitrogen (in mg TAN/L) does not exceed, more than once every three 

years on the average, the CCC calculated using the following equation:
231

 (

 

 

 

 ) ( ( ( )

))

Recalculated chronic criterion concentrations for the mussels absent, fish ELS protection 

necessary scenario across a range of temperatures and pH values are provided in Table N.8.

Unionid Mussels Absent, Early Life Stage (ELS) Protection Not Necessary 

One approach for setting a chronic criterion for mussels absent and fish ELS absent is to 

modify the criterion for mussels absent and fish ELS present. The four most sensitive genera for

the criterion to be modified are Lepomis (ELS), Musculium, Fluminicola, and Pimephales (ELS), 

which had yielded a criterion of 6.508 mg TAN/L at pH 7.0 and 20o C, or 0.9405 x the lowest 

GMCV (Lepomis). Since the Lepomis GMCV, 6.920 mg TAN/L, is based on ELS sensitivity,

consider that with ELS absent this value would increase to its juvenile and adult GMCV of 21.3 

mg TAN/L (from U.S. EPA 1999, page 75 GMCVs, translated from pH 8 to pH 7). In this case, 

Musculium, with GMCV 7.547 mg TAN/L, would now be the most sensitive genus in the 

dataset, such that at pH 7 and 20oC the criterion could be calculated as 0.9405 x 7.547 = 7.098 

mg TAN/L. Because Musculium remains the most sensitive genus throughout the full range of 

temperatures, the criterion follows the invertebrate temperature relationship, increasing with 

decreasing temperature until it reaches its maximum at the built-in 7oC plateau, which is 16.41 

mg TAN/L at pH 7, fully protective of the lowest juvenile-adult fish GMCV, that for Lepomis,

21.3 mg TAN/L shown above.

Mussels absent ELS protection not required at pH 7

 ( ( ( )))

Overall

 (

 

 

 

 ) ( ( ( ))

)

Recalculated chronic criterion concentrations for the mussels absent, fish ELS protection not 

required scenario across a range of temperatures and pH values are provided in Table N.9. A 
232

summary of the chronic criterion recalculations for all four mussel and fish ELS present and 

absent combinations at pH 7 and 20°C is included in Table N.7.
233

Table N.1. Temperature and pH-Dependent Values of the CMC (Acute Criterion Magnitude) – Unionid Mussels Present, 

Oncorhynchus Absent.

Temperature (°C)

pH 0-10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

6.5 51 48 44 41 37 34 32 29 27 25 23 21 19 18 16 15 14 13 12 11 9.9

6.6 49 46 42 39 36 33 30 28 26 24 22 20 18 17 16 14 13 12 11 10 9.5

6.7 46 44 40 37 34 31 29 27 24 22 21 19 18 16 15 14 13 12 11 9.8 9.0

6.8 44 41 38 35 32 30 27 25 23 21 20 18 17 15 14 13 12 11 10 9.2 8.5

6.9 41 38 35 32 30 28 25 23 21 20 18 17 15 14 13 12 11 10 9.4 8.6 7.9

7.0 38 35 33 30 28 25 23 21 20 18 17 15 14 13 12 11 10 9.4 8.6 7.9 7.3

7.1 34 32 30 27 25 23 21 20 18 17 15 14 13 12 11 10 9.3 8.5 7.9 7.2 6.7

7.2 31 29 27 25 23 21 19 18 16 15 14 13 12 11 9.8 9.1 8.3 7.7 7.1 6.5 6.0

7.3 27 26 24 22 20 18 17 16 14 13 12 11 10 9.5 8.7 8.0 7.4 6.8 6.3 5.8 5.3

7.4 24 22 21 19 18 16 15 14 13 12 11 9.8 9.0 8.3 7.7 7.0 6.5 6.0 5.5 5.1 4.7

7.5 21 19 18 17 15 14 13 12 11 10 9.2 8.5 7.8 7.2 6.6 6.1 5.6 5.2 4.8 4.4 4.0

7.6 18 17 15 14 13 12 11 10 9.3 8.6 7.9 7.3 6.7 6.2 5.7 5.2 4.8 4.4 4.1 3.8 3.5

7.7 15 14 13 12 11 10 9.3 8.6 7.9 7.3 6.7 6.2 5.7 5.2 4.8 4.4 4.1 3.8 3.5 3.2 2.9

7.8 13 12 11 10 9.3 8.5 7.9 7.2 6.7 6.1 5.6 5.2 4.8 4.4 4.0 3.7 3.4 3.2 2.9 2.7 2.5

7.9 11 9.9 9.1 8.4 7.7 7.1 6.6 3.0 5.6 5.1 4.7 4.3 4.0 3.7 3.4 3.1 2.9 2.6 2.4 2.2 2.1

8.0 8.8 8.2 7.6 7.0 6.4 5.9 5.4 5.0 4.6 4.2 3.9 3.6 3.3 3.0 2.8 2.6 2.4 2.2 2.0 1.9 1.7

8.1 7.2 6.8 6.3 5.8 5.3 4.9 4.5 4.1 3.8 3.5 3.2 3.0 2.7 2.5 2.3 2.1 2.0 1.8 1.7 1.5 1.4

8.2 6.0 5.6 5.2 4.8 4.4 4.0 3.7 3.4 3.1 2.9 2.7 2.4 2.3 2.1 1.9 1.8 1.6 1.5 1.4 1.3 1.2

8.3 4.9 4.6 4.3 3.9 3.6 3.3 3.1 2.8 2.6 2.4 2.2 2.0 1.9 1.7 1.6 1.4 1.3 1.2 1.1 1.0 0.96

8.4 4.1 3.8 3.5 3.2 3.0 2.7 2.5 2.3 2.1 2.0 1.8 1.7 1.5 1.4 1.3 1.2 1.1 1.0 0.93 0.86 0.79

8.5 3.3 3.1 2.9 2.7 2.4 2.3 2.1 1.9 1.8 1.6 1.5 1.4 1.3 1.2 1.1 0.98 0.90 0.83 0.77 0.71 0.65

8.6 2.8 2.6 2.4 2.2 2.0 1.9 1.7 1.6 1.5 1.3 1.2 1.1 1.0 0.96 0.88 0.81 0.75 0.69 0.63 0.58 0.54

8.7 2.3 2.2 2.0 1.8 1.7 1.6 1.4 1.3 1.2 1.1 1.0 0.94 0.87 0.80 0.74 0.68 0.62 0.57 0.53 0.49 0.45

8.8 1.9 1.8 1.7 1.5 1.4 1.3 1.2 1.1 1.0 0.93 0.86 0.79 0.73 0.67 0.62 0.57 0.52 0.48 0.44 0.41 0.37

8.9 1.6 1.5 1.4 1.3 1.2 1.1 1.0 0.93 0.85 0.79 0.72 0.67 0.61 0.56 0.52 0.48 0.44 0.40 0.37 0.34 0.32

9.0 1.4 1.3 1.2 1.1 1.0 0.93 0.86 0.79 0.73 0.67 0.62 0.57 0.52 0.48 0.44 0.41 0.37 0.34 0.32 0.29 0.27
234

Table N.2. Acute Data Without Mussels: Comparison of the Four Taxa Used to Calculate the FAV and CMC in the 1999 

AWQC and this Updated 2013 AWQC Excluding Data for Freshwater Unionid Mussels.

1999 Draft Update Acute Criterion (CMC) Magnitude (Salmonids 

[Oncorhynchus spp.] present)

2013 Final Acute Criterion (CMC) Magnitude excluding 

Mussels (Salmonids [Oncorhynchus spp.] absent)

Species

GMAV

pH 8.0,

T=25°C

(mg TAN/L)

GMAV

pH 7.0,

T=20°C

(mg TAN/L) Species

GMAV

pH 7.0,

T=20°C

(mg TAN/L)

Oncorhynchus sp. (salmonids), includes: O. 

aquabonita, O. clarkii, O. gorbuscha, O. 

kisutch*, O. mykiss*, and O. tshawytscha*

21.95 99.15 Golden shiner, 

Notemigonus crysoleucas

63.02

Orangethroat darter, 

Etheostoma spectabile

17.96 74.25 Pebblesnail, 

Fluminicola sp.

62.15

Golden shiner, 

Notemigonus crysoleucas

14.67 63.02 Lost River sucker, 

Deltistes luxatus*

56.62

Mountain whitefish, 

Prosopium williamsoni

12.11 51.93 Mountain whitefish, 

Prosopium williamsoni

51.93

FAV 11.23 48.21 FAV 76

CMC 5.6 24 CMC 38**

*Federally-listed as endangered or threatened species 

**CMC Excluding mussels, with Oncorhynchus present is 24 mg TAN/L to protect the recreationally and commercially important species Rainbow Trout. When 

Oncorhynchus is absent, the CMC is based on the mountain whitefish and is calculated by the ratio of the CMC to the lowest GMAV in the complete acute dataset (0.7249) 

times the lowest GMAV in the dataset excluding mussels (51.93 mg TAN/L for mountain whitefish) which results in a CMC of 37.65 mg TAN/L at pH 7 and 20°C.
235

Table N.3. Temperature and pH-Dependent Values of the CMC (Acute Criterion Magnitude) – Unionid Mussels Absent and 

Oncorhynchus Present.

Temperature (°C)

pH 0-14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

6.5 33 33 33 33 33 33 33 33 33 33 33 33 33 33 31 29 27

6.6 31 31 31 31 31 31 31 31 31 31 31 31 31 31 30 28 26

6.7 30 30 30 30 30 30 30 30 30 30 30 30 30 30 29 26 24

6.8 28 28 28 28 28 28 28 28 28 28 28 28 28 28 27 25 23

6.9 26 26 26 26 26 26 26 26 26 26 26 26 26 26 25 23 21

7.0 24 24 24 24 24 24 24 24 24 24 24 24 24 24 23 21 20

7.1 22 22 22 22 22 22 22 22 22 22 22 22 22 22 21 19 18

7.2 20 20 20 20 20 20 20 20 20 20 20 20 20 20 19 17 16

7.3 18 18 18 18 18 18 18 18 18 18 18 18 18 18 17 16 14

7.4 15 15 15 15 15 15 15 15 15 15 15 15 15 15 15 14 13

7.5 13 13 13 13 13 13 13 13 13 13 13 13 13 13 13 12 11

7.6 11 11 11 11 11 11 11 11 11 11 11 11 11 11 11 10 9.3

7.7 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.6 9.3 8.6 7.9

7.8 8.1 8.1 8.1 8.1 8.1 8.1 8.1 8.1 8.1 8.1 8.1 8.1 8.1 8.1 7.8 7.2 6.6

7.9 6.8 6.8 6.8 6.8 6.8 6.8 6.8 6.8 6.8 6.8 6.8 6.8 6.8 6.8 6.5 6.0 5.5

8.0 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.4 5.0 4.6

8.1 4.6 4.6 4.6 4.6 4.6 4.6 4.6 4.6 4.6 4.6 4.6 4.6 4.6 4.6 4.5 4.1 3.8

8.2 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.8 3.7 3.4 3.1

8.3 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.2 3.0 2.8 2.6

8.4 2.6 2.6 2.6 2.6 2.6 2.6 2.6 2.6 2.6 2.6 2.6 2.6 2.6 2.6 2.5 2.3 2.1

8.5 2.1 2.1 2.1 2.1 2.1 2.1 2.1 2.1 2.1 2.1 2.1 2.1 2.1 2.1 2.1 1.9 1.8

8.6 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.7 1.6 1.4

8.7 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.5 1.4 1.3 1.2

8.8 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.1 1.0

8.9 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 0.92 0.85

9.0 0.88 0.88 0.88 0.88 0.88 0.88 0.88 0.88 0.88 0.88 0.88 0.88 0.88 0.88 0.85 0.78 0.72
236

Table N.4. Temperature and pH-Dependent Values of the CMC (Acute Criterion Magnitude) – Unionid Mussels Absent and 

Oncorhynchus Absent.

Temperature (°C)

pH 0-14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

6.5 51 51 51 51 51 51 51 51 51 48 44 40 37 34 31 29 27

6.6 49 49 49 49 49 49 49 49 49 46 42 39 36 33 30 28 26

6.7 46 46 46 46 46 46 46 46 46 43 40 37 34 31 29 26 24

6.8 44 44 44 44 44 44 44 44 44 41 38 35 32 29 27 25 23

6.9 41 41 41 41 41 41 41 41 41 38 35 32 30 27 25 23 21

7.0 38 38 38 38 38 38 38 38 38 35 32 30 27 25 23 21 20

7.1 34 34 34 34 34 34 34 34 34 32 29 27 25 23 21 19 18

7.2 31 31 31 31 31 31 31 31 31 29 26 24 22 21 19 17 16

7.3 27 27 27 27 27 27 27 27 27 26 23 22 20 18 17 16 14

7.4 24 24 24 24 24 24 24 24 24 22 21 19 17 16 15 14 13

7.5 21 21 21 21 21 21 21 21 21 19 18 16 15 14 13 12 11

7.6 18 18 18 18 18 18 18 18 18 17 15 14 13 12 11 10 9.3

7.7 15 15 15 15 15 15 15 15 15 14 13 12 11 10 9.3 8.6 7.9

7.8 13 13 13 13 13 13 13 13 13 12 11 10 9.2 8.5 7.8 7.2 6.6

7.9 11 11 11 11 11 11 11 11 11 9.9 9.1 8.4 7.7 7.1 6.5 6.0 5.5

8.0 8.8 8.8 8.8 8.8 8.8 8.8 8.8 8.8 8.8 8.2 7.5 6.9 6.4 5.9 5.4 5.0 4.6

8.1 7.3 7.3 7.3 7.3 7.3 7.3 7.3 7.3 7.3 6.8 6.2 5.7 5.3 4.9 4.5 4.1 3.8

8.2 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 6.0 5.6 5.1 4.7 4.4 4.0 3.7 3.4 3.1

8.3 4.9 4.9 4.9 4.9 4.9 4.9 4.9 4.9 4.9 4.6 4.2 3.9 3.6 3.3 3.0 2.8 2.6

8.4 4.1 4.1 4.1 4.1 4.1 4.1 4.1 4.1 4.1 3.8 3.4 3.2 3.0 2.7 2.5 2.3 2.1

8.5 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.3 3.1 2.9 2.6 2.4 2.2 2.1 1.9 1.8

8.6 2.8 2.8 2.8 2.8 2.8 2.8 2.8 2.8 2.8 2.6 2.4 2.2 2.0 1.9 1.7 1.6 1.4

8.7 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.2 2.0 1.8 1.7 1.5 1.4 1.3 1.2

8.8 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.9 1.8 1.7 1.5 1.4 1.3 1.2 1.1 1.0

8.9 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.6 1.5 1.4 1.3 1.2 1.1 1.0 0.92 0.85

9.0 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.3 1.2 1.1 1.0 0.93 0.85 0.78 0.72
237

Table N.5. 2013 Acute Criterion Recalculations for Site-specific Criteria.

Acute Criterion Duration

(1 hr average)

at pH 7 and 20°C

(mg TAN/L)

Acute Criterion Magnitude 

(CMC) 

Oncorhynchus spp.

(Rainbow Trout) Present

Acute Criterion Magnitude 

(CMC) 

Oncorhynchus spp.

(Rainbow Trout) Absent

Mussels Present 17 17

Mussels Absent 24 38

Frequency: Criteria values not to be exceeded more than once in three years.

Table N.6. Chronic Dataset Without Mussels: Comparison of the Four Taxa used to 

Calculate the CCC in the 1999 AWQC and this Updated 2013 AWQC Excluding Data for 

Freshwater Unionid Mussels.

1999 Draft Update Chronic Criterion (CCC) Magnitude 2013 Final Chronic Criterion (CCC) 

Magnitude excluding mussels 

Species

GMCV

pH 8.0,

T=25°C

(mg TAN/L)

GMCV

pH 7.0,

T=20°C

(mg TAN/L) Species

GMCV

pH 7.0,

T=20°C

(mg TAN/L)

Fathead minnow,

Pimephales promelas 3.09 7.503 Fathead minnow,Pimephales promelas 9.187

Lepomis sp. 

(Centrarchidae), includes:

Bluegill sunfish, L. 

macrochirus, and Green 

sunfish, L. cyanellus

2.85 6.92 Pebblesnail,

Fluminicola sp.

7.828

Long fingernailclam,

Musculium transversum <2.26 7.547 Long fingernailclam,Musculium transversum 7.547

Amphipod,

Hyalella azteca <1.45 4.865

Lepomis sp.

(Centrarchidae), includes:

Bluegill, L. macrochirus and 

Green sunfish, L. cyanellus

6.920

CCC 1.2 4.5* CCC 6.5

*Based on data renormalized to pH 7.0 and T 20°C
238

Table N.7. Chronic Criterion Recalculations for Site-Specific Criteria.

Chronic Criterion Duration

(30-day average)

at pH 7 and 20°C

(mg TAN/L)

Chronic Criterion 

Magnitude (CCC) 

Fish ELS Present

Chronic Criterion 

Magnitude (CCC)

Fish ELS Absent

Mussels Present 1.9 1.9

Mussels Absent 6.5 7.1

Not to exceed 2.5 times the CCC as a 4-day average within the 30-day averaging period.

Frequency: Criteria values not to be exceeded more than once in three years.
239

Table N.8. Temperature and pH-Dependent Values of the CCC (Chronic Criterion Magnitude) – Mussels Absent and Early 

Life Stage (ELS) Protection Necessary.

Temperature (°C)

pH 0-14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

6.5 7.3 7.3 7.3 7.3 7.3 7.3 7.3 7.3 7.0 6.6 6.2 5.8 5.4 5.1 4.8 4.5 4.2

6.6 7.2 7.2 7.2 7.2 7.2 7.2 7.2 7.2 6.9 6.5 6.1 5.7 5.4 5.0 4.7 4.4 4.1

6.7 7.1 7.1 7.1 7.1 7.1 7.1 7.1 7.1 6.8 6.4 6.0 5.6 5.3 4.9 4.6 4.3 4.1

6.8 6.9 6.9 6.9 6.9 6.9 6.9 6.9 6.9 6.6 6.2 5.8 5.5 5.1 4.8 4.5 4.2 4.0

6.9 6.7 6.7 6.7 6.7 6.7 6.7 6.7 6.7 6.5 6.1 5.7 5.3 5.0 4.7 4.4 4.1 3.9

7.0 6.5 6.5 6.5 6.5 6.5 6.5 6.5 6.5 6.2 5.8 5.5 5.1 4.8 4.5 4.2 4.0 3.7

7.1 6.2 6.2 6.2 6.2 6.2 6.2 6.2 6.2 6.0 5.6 5.3 4.9 4.6 4.3 4.1 3.8 3.6

7.2 5.9 5.9 5.9 5.9 5.9 5.9 5.9 5.9 5.7 5.3 5.0 4.7 4.4 4.1 3.9 3.6 3.4

7.3 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.6 5.4 5.0 4.7 4.4 4.1 3.9 3.6 3.4 3.2

7.4 5.2 5.2 5.2 5.2 5.2 5.2 5.2 5.2 5.0 4.7 4.4 4.1 3.9 3.6 3.4 3.2 3.0

7.5 4.8 4.8 4.8 4.8 4.8 4.8 4.8 4.8 4.6 4.3 4.1 3.8 3.6 3.3 3.1 2.9 2.8

7.6 4.4 4.4 4.4 4.4 4.4 4.4 4.4 4.4 4.2 3.9 3.7 3.5 3.2 3.0 2.9 2.7 2.5

7.7 3.9 3.9 3.9 3.9 3.9 3.9 3.9 3.9 3.8 3.5 3.3 3.1 2.9 2.7 2.6 2.4 2.3

7.8 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.5 3.4 3.2 3.0 2.8 2.6 2.4 2.3 2.1 2.0

7.9 3.1 3.1 3.1 3.1 3.1 3.1 3.1 3.1 3.0 2.8 2.6 2.4 2.3 2.1 2.0 1.9 1.8

8.0 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.7 2.6 2.4 2.3 2.1 2.0 1.9 1.7 1.6 1.5

8.1 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.2 2.1 1.9 1.8 1.7 1.6 1.5 1.4 1.3

8.2 2.0 2.0 2.0 2.0 2.0 2.0 2.0 2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1

8.3 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.6 1.5 1.4 1.3 1.2 1.2 1.1 1.0 0.96

8.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.4 1.3 1.2 1.1 1.1 0.99 0.93 0.87 0.81

8.5 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.1 1.0 0.95 0.89 0.83 0.78 0.73 0.69

8.6 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 0.97 0.91 0.85 0.80 0.75 0.70 0.66 0.62 0.58

8.7 0.86 0.86 0.86 0.86 0.86 0.86 0.86 0.86 0.82 0.77 0.72 0.68 0.64 0.60 0.56 0.52 0.49

8.8 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.73 0.70 0.65 0.61 0.58 0.54 0.51 0.47 0.44 0.42

8.9 0.62 0.62 0.62 0.62 0.62 0.62 0.62 0.62 0.60 0.56 0.52 0.49 0.46 0.43 0.41 0.38 0.36

9.0 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.54 0.51 0.48 0.45 0.42 0.40 0.37 0.35 0.33 0.31
240

Table N.9. Temperature and pH-Dependent Values of the CCC (Chronic Criterion Magnitude) – Mussels Absent and Early 

Life Stage (ELS) Protection not Necessary.

Temperature (°C)

pH 0-7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30

6.5 19 17 16 15 14 13 13 12 11 10 9.7 9.1 8.5 8.0 7.5 7.0 6.6 6.2 5.8 5.4 5.1 4.8 4.5 4.2

6.6 18 17 16 15 14 13 12 12 11 10 9.6 9.0 8.4 7.9 7.4 6.9 6.5 6.1 5.7 5.4 5.0 4.7 4.4 4.1

6.7 18 17 16 15 14 13 12 11 11 10 9.4 8.8 8.3 7.7 7.3 6.8 6.4 6.0 5.6 5.3 4.9 4.6 4.3 4.1

6.8 17 16 15 14 14 13 12 11 10 9.8 9.2 8.6 8.1 7.6 7.1 6.7 6.2 5.8 5.5 5.1 4.8 4.5 4.2 4.0

6.9 17 16 15 14 13 12 12 11 10 9.5 8.9 8.4 7.8 7.4 6.9 6.5 6.1 5.7 5.3 5.0 4.7 4.4 4.1 3.9

7.0 16 15 14 14 13 12 11 10 9.8 9.2 8.6 8.1 7.6 7.1 6.7 6.2 5.9 5.5 5.1 4.8 4.5 4.2 4.0 3.7

7.1 16 15 14 13 12 11 11 10 9.4 8.8 8.3 7.7 7.3 6.8 6.4 6.0 5.6 5.3 4.9 4.6 4.3 4.1 3.8 3.6

7.2 15 14 13 12 12 11 10 9.5 9.0 8.4 7.9 7.4 6.9 6.5 6.1 5.7 5.3 5.0 4.7 4.4 4.1 3.9 3.6 3.4

7.3 14 13 12 12 11 10 9.6 9.0 8.4 7.9 7.4 6.9 6.5 6.1 5.7 5.4 5.0 4.7 4.4 4.1 3.9 3.6 3.4 3.2

7.4 13 12 12 11 10 9.5 9.0 8.4 7.9 7.4 6.9 6.5 6.1 5.7 5.3 5.0 4.7 4.4 4.1 3.9 3.6 3.4 3.2 3.0

7.5 12 11 11 10 9.4 8.8 8.2 7.7 7.2 6.8 6.4 6.0 5.6 5.2 4.9 4.6 4.3 4.1 3.8 3.6 3.3 3.1 2.9 2.8

7.6 11 10 10 9.1 8.5 8.0 7.5 7.0 6.6 6.2 5.8 5.4 5.1 4.8 4.5 4.2 3.9 3.7 3.5 3.2 3.0 2.9 2.7 2.5

7.7 9.9 9.3 8.7 8.1 7.7 7.2 6.8 6.3 5.9 5.6 5.2 4.9 4.6 4.3 4.0 3.8 3.5 3.3 3.1 2.9 2.7 2.6 2.4 2.3

7.8 8.8 8.3 7.8 7.3 6.8 6.4 6.0 5.6 5.3 5.0 4.6 4.4 4.1 3.8 3.6 3.4 3.2 3.0 2.8 2.6 2.4 2.3 2.1 2.0

7.9 7.8 7.3 6.8 6.4 6.0 5.6 5.3 5.0 4.6 4.4 4.1 3.8 3.6 3.4 3.2 3.0 2.8 2.6 2.4 2.3 2.1 2.0 1.9 1.8

8.0 6.8 6.3 6.0 5.6 5.2 4.9 4.6 4.3 4.0 3.8 3.6 3.3 3.1 2.9 2.7 2.6 2.4 2.3 2.1 2.0 1.9 1.7 1.6 1.5

8.1 5.8 5.5 5.1 4.8 4.5 4.2 4.0 3.7 3.5 3.3 3.1 2.9 2.7 2.5 2.4 2.2 2.1 2.0 1.8 1.7 1.6 1.5 1.4 1.3

8.2 5.0 4.7 4.4 4.1 3.9 3.6 3.4 3.2 3.0 2.8 2.6 2.5 2.3 2.2 2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1

8.3 4.2 4.0 3.7 3.5 3.3 3.1 2.9 2.7 2.5 2.4 2.2 2.1 2.0 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.2 1.1 1.0 0.96

8.4 3.6 3.4 3.2 3.0 2.8 2.6 2.4 2.3 2.1 2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.1 0.99 0.92 0.87 0.81

8.5 3.0 2.8 2.7 2.5 2.3 2.2 2.1 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.2 1.1 1.0 0.95 0.89 0.83

3

0.78 0.73 0.69

8.6 2.6 2.4 2.2 2.1 2.0 1.9 1.7 1.6 1.5 1.4 1.3 1.3 1.2 1.1 1.0 0.97 0.91 0.85 0.80 0.75 0.70 0.66 0.62 0.58

8.7 2.2 2.0 1.9 1.8 1.7 1.6 1.5 1.4 1.3 1.2 1.1 1.1 1.0 0.93 0.88 0.82 0.77 0.72 0.68 0.63 0.60 0.56 0.52 0.49

8.8 1.8 1.7 1.6 1.5 1.4 1.3 1.3 1.2 1.1 1.0 0.96 0.90 0.85 0.79 0.74 0.70 0.65 0.61 0.58 0.54 0.51 0.47 0.44 0.42

8.9 1.6 1.5 1.4 1.3 1.2 1.1 1.1 1.0 0.94 0.88 0.82 0.77 0.72 0.68 0.64 0.60 0.56 0.52 0.49 0.46 0.43 0.40 0.38 0.36

9.0 1.4 1.3 1.2 1.1 1.0 0.98 0.92 0.86

6

0.81 0.76 0.71 0.66 0.62 0.58 0.55 0.51 0.48 0.45 0.42 0.40 0.37 0.35 0.33 0.31
241

Figure N.1. Comparison of the 2013 CMC Extrapolated Across a Temperature Gradient 

at pH 7 Accounting for the Presence or Absence of Unionid Mussels and the Presence or 

Absence of Oncorhynchus.

Temperature (°C)

0 5 10 15 20 25 30

CMC at pH 7 (mg TAN/L)

0

10

20

30

40

Mussels Present, Oncorhynchus Absent

Mussels Present, Oncorhynchus Present

Mussels Absent, Oncorhynchus Absent

Mussels Absent, Oncorhynchus Present
242

Figure N.2. Comparison of the 2013 CCC Extrapolated Across a Temperature Gradient at 

pH 7 Accounting for the Presence or Absence of Mussels and/or the Need for Early Life 

Stage (ELS) Protection of Fish Species.

Temperature (°C)

0 5 10 15 20 25 30

CCC at pH 7(mg TAN/L)

0

2

4

6

8

10

12

14

16

18

Mussels Absent, ELS Present

Mussels Absent, ELS Absent

Mussels Present, ELS Present

or Absent